parser: add stub class that will host alias parsing and expansion

This class will keep syntax rules that are necessary to parse and expand
aliases. The implementations will be extracted from the revset module. In
order to make the porting easier, this class keeps parsedecl and parsedefn
separately, which will be unified later. Also, getlist and funcnode will
be refactored by future patches for better handling of the template aliases.

The following public functions will be added:

  aliasrules.build(decl, defn) -> aliasobj
    parse decl and defn into an object that keeps alias name, arguments
    and replacement tree.
  aliasrules.buildmap(aliasitems) -> aliasdict
    helper to build() a dict of alias objects from a list of (decl, defn)
  aliasrules.expand(aliasdict, tree) -> tree
    expand aliases in tree recursively

Because these functions aren't introduced by this series, there would remain
a few wrapper functions in the revset module. These ugly wrappers should be
eliminated by the next series.

This class is considered an inheritable namespace, which will host only
class/static methods. That's because it won't have no object-scope variables.
I'm not a big fan of using class as a syntax sugar, but I admit it can improve
code readability at some level. So let's give it a try.

mercurial/parser.py

@@ -1,230 +1,266
 # parser.py - simple top-down operator precedence parser for mercurial
 #
 # Copyright 2010 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 # see http://effbot.org/zone/simple-top-down-parsing.htm and
 # http://eli.thegreenplace.net/2010/01/02/top-down-operator-precedence-parsing/
 # for background
 
 # takes a tokenizer and elements
 # tokenizer is an iterator that returns (type, value, pos) tuples
 # elements is a mapping of types to binding strength, primary, prefix, infix
 # and suffix actions
 # an action is a tree node name, a tree label, and an optional match
 # __call__(program) parses program into a labeled tree
 
 from __future__ import absolute_import
 
 from .i18n import _
 from . import error
 
 class parser(object):
     def __init__(self, elements, methods=None):
         self._elements = elements
         self._methods = methods
         self.current = None
     def _advance(self):
         'advance the tokenizer'
         t = self.current
         self.current = next(self._iter, None)
         return t
     def _hasnewterm(self):
         'True if next token may start new term'
         return any(self._elements[self.current[0]][1:3])
     def _match(self, m):
         'make sure the tokenizer matches an end condition'
         if self.current[0] != m:
             raise error.ParseError(_("unexpected token: %s") % self.current[0],
                                    self.current[2])
         self._advance()
     def _parseoperand(self, bind, m=None):
         'gather right-hand-side operand until an end condition or binding met'
         if m and self.current[0] == m:
             expr = None
         else:
             expr = self._parse(bind)
         if m:
             self._match(m)
         return expr
     def _parse(self, bind=0):
         token, value, pos = self._advance()
         # handle prefix rules on current token, take as primary if unambiguous
         primary, prefix = self._elements[token][1:3]
         if primary and not (prefix and self._hasnewterm()):
             expr = (primary, value)
         elif prefix:
             expr = (prefix[0], self._parseoperand(*prefix[1:]))
         else:
             raise error.ParseError(_("not a prefix: %s") % token, pos)
         # gather tokens until we meet a lower binding strength
         while bind < self._elements[self.current[0]][0]:
             token, value, pos = self._advance()
             # handle infix rules, take as suffix if unambiguous
             infix, suffix = self._elements[token][3:]
             if suffix and not (infix and self._hasnewterm()):
                 expr = (suffix[0], expr)
             elif infix:
                 expr = (infix[0], expr, self._parseoperand(*infix[1:]))
             else:
                 raise error.ParseError(_("not an infix: %s") % token, pos)
         return expr
     def parse(self, tokeniter):
         'generate a parse tree from tokens'
         self._iter = tokeniter
         self._advance()
         res = self._parse()
         token, value, pos = self.current
         return res, pos
     def eval(self, tree):
         'recursively evaluate a parse tree using node methods'
         if not isinstance(tree, tuple):
             return tree
         return self._methods[tree[0]](*[self.eval(t) for t in tree[1:]])
     def __call__(self, tokeniter):
         'parse tokens into a parse tree and evaluate if methods given'
         t = self.parse(tokeniter)
         if self._methods:
             return self.eval(t)
         return t
 
 def buildargsdict(trees, funcname, keys, keyvaluenode, keynode):
     """Build dict from list containing positional and keyword arguments
 
     Invalid keywords or too many positional arguments are rejected, but
     missing arguments are just omitted.
     """
     if len(trees) > len(keys):
         raise error.ParseError(_("%(func)s takes at most %(nargs)d arguments")
                                % {'func': funcname, 'nargs': len(keys)})
     args = {}
     # consume positional arguments
     for k, x in zip(keys, trees):
         if x[0] == keyvaluenode:
             break
         args[k] = x
     # remainder should be keyword arguments
     for x in trees[len(args):]:
         if x[0] != keyvaluenode or x[1][0] != keynode:
             raise error.ParseError(_("%(func)s got an invalid argument")
                                    % {'func': funcname})
         k = x[1][1]
         if k not in keys:
             raise error.ParseError(_("%(func)s got an unexpected keyword "
                                      "argument '%(key)s'")
                                    % {'func': funcname, 'key': k})
         if k in args:
             raise error.ParseError(_("%(func)s got multiple values for keyword "
                                      "argument '%(key)s'")
                                    % {'func': funcname, 'key': k})
         args[k] = x[2]
     return args
 
 def unescapestr(s):
     try:
         return s.decode("string_escape")
     except ValueError as e:
         # mangle Python's exception into our format
         raise error.ParseError(str(e).lower())
 
 def _prettyformat(tree, leafnodes, level, lines):
     if not isinstance(tree, tuple) or tree[0] in leafnodes:
         lines.append((level, str(tree)))
     else:
         lines.append((level, '(%s' % tree[0]))
         for s in tree[1:]:
             _prettyformat(s, leafnodes, level + 1, lines)
         lines[-1:] = [(lines[-1][0], lines[-1][1] + ')')]
 
 def prettyformat(tree, leafnodes):
     lines = []
     _prettyformat(tree, leafnodes, 0, lines)
     output = '\n'.join(('  ' * l + s) for l, s in lines)
     return output
 
 def simplifyinfixops(tree, targetnodes):
     """Flatten chained infix operations to reduce usage of Python stack
 
     >>> def f(tree):
     ...     print prettyformat(simplifyinfixops(tree, ('or',)), ('symbol',))
     >>> f(('or',
     ...     ('or',
     ...       ('symbol', '1'),
     ...       ('symbol', '2')),
     ...     ('symbol', '3')))
     (or
       ('symbol', '1')
       ('symbol', '2')
       ('symbol', '3'))
     >>> f(('func',
     ...     ('symbol', 'p1'),
     ...     ('or',
     ...       ('or',
     ...         ('func',
     ...           ('symbol', 'sort'),
     ...           ('list',
     ...             ('or',
     ...               ('or',
     ...                 ('symbol', '1'),
     ...                 ('symbol', '2')),
     ...               ('symbol', '3')),
     ...             ('negate',
     ...               ('symbol', 'rev')))),
     ...         ('and',
     ...           ('symbol', '4'),
     ...           ('group',
     ...             ('or',
     ...               ('or',
     ...                 ('symbol', '5'),
     ...                 ('symbol', '6')),
     ...               ('symbol', '7'))))),
     ...       ('symbol', '8'))))
     (func
       ('symbol', 'p1')
       (or
         (func
           ('symbol', 'sort')
           (list
             (or
               ('symbol', '1')
               ('symbol', '2')
               ('symbol', '3'))
             (negate
               ('symbol', 'rev'))))
         (and
           ('symbol', '4')
           (group
             (or
               ('symbol', '5')
               ('symbol', '6')
               ('symbol', '7'))))
         ('symbol', '8')))
     """
     if not isinstance(tree, tuple):
         return tree
     op = tree[0]
     if op not in targetnodes:
         return (op,) + tuple(simplifyinfixops(x, targetnodes) for x in tree[1:])
 
     # walk down left nodes taking each right node. no recursion to left nodes
     # because infix operators are left-associative, i.e. left tree is deep.
     # e.g. '1 + 2 + 3' -> (+ (+ 1 2) 3) -> (+ 1 2 3)
     simplified = []
     x = tree
     while x[0] == op:
         l, r = x[1:]
         simplified.append(simplifyinfixops(r, targetnodes))
         x = l
     simplified.append(simplifyinfixops(x, targetnodes))
     simplified.append(op)
     return tuple(reversed(simplified))
 
 def parseerrordetail(inst):
     """Compose error message from specified ParseError object
     """
     if len(inst.args) > 1:
         return _('at %s: %s') % (inst.args[1], inst.args[0])
     else:
         return inst.args[0]
+
+class basealiasrules(object):
+    """Parsing and expansion rule set of aliases
+
+    This is a helper for fileset/revset/template aliases. A concrete rule set
+    should be made by sub-classing this and implementing class/static methods.
+
+    It supports alias expansion of symbol and funciton-call styles::
+
+        # decl = defn
+        h = heads(default)
+        b($1) = ancestors($1) - ancestors(default)
+    """
+    # typically a config section, which will be included in error messages
+    _section = None
+    # tags of symbol and function nodes
+    _symbolnode = 'symbol'
+    _funcnode = 'func'
+
+    def __new__(cls):
+        raise TypeError("'%s' is not instantiatable" % cls.__name__)
+
+    @staticmethod
+    def _parsedecl(spec):
+        """Parse an alias name and arguments"""
+        raise NotImplementedError
+
+    @staticmethod
+    def _parsedefn(spec):
+        """Parse an alias definition"""
+        raise NotImplementedError
+
+    @staticmethod
+    def _getlist(tree):
+        """Extract a list of arguments from parsed tree"""
+        raise NotImplementedError

mercurial/revset.py

@@ -1,3594 +1,3599
 # revset.py - revision set queries for mercurial
 #
 # Copyright 2010 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import heapq
 import re
 
 from .i18n import _
 from . import (
     destutil,
     encoding,
     error,
     hbisect,
     match as matchmod,
     node,
     obsolete as obsmod,
     parser,
     pathutil,
     phases,
     registrar,
     repoview,
     util,
 )
 
 def _revancestors(repo, revs, followfirst):
     """Like revlog.ancestors(), but supports followfirst."""
     if followfirst:
         cut = 1
     else:
         cut = None
     cl = repo.changelog
 
     def iterate():
         revs.sort(reverse=True)
         irevs = iter(revs)
         h = []
 
         inputrev = next(irevs, None)
         if inputrev is not None:
             heapq.heappush(h, -inputrev)
 
         seen = set()
         while h:
             current = -heapq.heappop(h)
             if current == inputrev:
                 inputrev = next(irevs, None)
                 if inputrev is not None:
                     heapq.heappush(h, -inputrev)
             if current not in seen:
                 seen.add(current)
                 yield current
                 for parent in cl.parentrevs(current)[:cut]:
                     if parent != node.nullrev:
                         heapq.heappush(h, -parent)
 
     return generatorset(iterate(), iterasc=False)
 
 def _revdescendants(repo, revs, followfirst):
     """Like revlog.descendants() but supports followfirst."""
     if followfirst:
         cut = 1
     else:
         cut = None
 
     def iterate():
         cl = repo.changelog
         # XXX this should be 'parentset.min()' assuming 'parentset' is a
         # smartset (and if it is not, it should.)
         first = min(revs)
         nullrev = node.nullrev
         if first == nullrev:
             # Are there nodes with a null first parent and a non-null
             # second one? Maybe. Do we care? Probably not.
             for i in cl:
                 yield i
         else:
             seen = set(revs)
             for i in cl.revs(first + 1):
                 for x in cl.parentrevs(i)[:cut]:
                     if x != nullrev and x in seen:
                         seen.add(i)
                         yield i
                         break
 
     return generatorset(iterate(), iterasc=True)
 
 def _reachablerootspure(repo, minroot, roots, heads, includepath):
     """return (heads(::<roots> and ::<heads>))
 
     If includepath is True, return (<roots>::<heads>)."""
     if not roots:
         return []
     parentrevs = repo.changelog.parentrevs
     roots = set(roots)
     visit = list(heads)
     reachable = set()
     seen = {}
     # prefetch all the things! (because python is slow)
     reached = reachable.add
     dovisit = visit.append
     nextvisit = visit.pop
     # open-code the post-order traversal due to the tiny size of
     # sys.getrecursionlimit()
     while visit:
         rev = nextvisit()
         if rev in roots:
             reached(rev)
             if not includepath:
                 continue
         parents = parentrevs(rev)
         seen[rev] = parents
         for parent in parents:
             if parent >= minroot and parent not in seen:
                 dovisit(parent)
     if not reachable:
         return baseset()
     if not includepath:
         return reachable
     for rev in sorted(seen):
         for parent in seen[rev]:
             if parent in reachable:
                 reached(rev)
     return reachable
 
 def reachableroots(repo, roots, heads, includepath=False):
     """return (heads(::<roots> and ::<heads>))
 
     If includepath is True, return (<roots>::<heads>)."""
     if not roots:
         return baseset()
     minroot = roots.min()
     roots = list(roots)
     heads = list(heads)
     try:
         revs = repo.changelog.reachableroots(minroot, heads, roots, includepath)
     except AttributeError:
         revs = _reachablerootspure(repo, minroot, roots, heads, includepath)
     revs = baseset(revs)
     revs.sort()
     return revs
 
 elements = {
     # token-type: binding-strength, primary, prefix, infix, suffix
     "(": (21, None, ("group", 1, ")"), ("func", 1, ")"), None),
     "##": (20, None, None, ("_concat", 20), None),
     "~": (18, None, None, ("ancestor", 18), None),
     "^": (18, None, None, ("parent", 18), ("parentpost", 18)),
     "-": (5, None, ("negate", 19), ("minus", 5), None),
     "::": (17, None, ("dagrangepre", 17), ("dagrange", 17),
            ("dagrangepost", 17)),
     "..": (17, None, ("dagrangepre", 17), ("dagrange", 17),
            ("dagrangepost", 17)),
     ":": (15, "rangeall", ("rangepre", 15), ("range", 15), ("rangepost", 15)),
     "not": (10, None, ("not", 10), None, None),
     "!": (10, None, ("not", 10), None, None),
     "and": (5, None, None, ("and", 5), None),
     "&": (5, None, None, ("and", 5), None),
     "%": (5, None, None, ("only", 5), ("onlypost", 5)),
     "or": (4, None, None, ("or", 4), None),
     "|": (4, None, None, ("or", 4), None),
     "+": (4, None, None, ("or", 4), None),
     "=": (3, None, None, ("keyvalue", 3), None),
     ",": (2, None, None, ("list", 2), None),
     ")": (0, None, None, None, None),
     "symbol": (0, "symbol", None, None, None),
     "string": (0, "string", None, None, None),
     "end": (0, None, None, None, None),
 }
 
 keywords = set(['and', 'or', 'not'])
 
 # default set of valid characters for the initial letter of symbols
 _syminitletters = set(c for c in [chr(i) for i in xrange(256)]
                       if c.isalnum() or c in '._@' or ord(c) > 127)
 
 # default set of valid characters for non-initial letters of symbols
 _symletters = set(c for c in  [chr(i) for i in xrange(256)]
                   if c.isalnum() or c in '-._/@' or ord(c) > 127)
 
 def tokenize(program, lookup=None, syminitletters=None, symletters=None):
     '''
     Parse a revset statement into a stream of tokens
 
     ``syminitletters`` is the set of valid characters for the initial
     letter of symbols.
 
     By default, character ``c`` is recognized as valid for initial
     letter of symbols, if ``c.isalnum() or c in '._@' or ord(c) > 127``.
 
     ``symletters`` is the set of valid characters for non-initial
     letters of symbols.
 
     By default, character ``c`` is recognized as valid for non-initial
     letters of symbols, if ``c.isalnum() or c in '-._/@' or ord(c) > 127``.
 
     Check that @ is a valid unquoted token character (issue3686):
     >>> list(tokenize("@::"))
     [('symbol', '@', 0), ('::', None, 1), ('end', None, 3)]
 
     '''
     if syminitletters is None:
         syminitletters = _syminitletters
     if symletters is None:
         symletters = _symletters
 
     if program and lookup:
         # attempt to parse old-style ranges first to deal with
         # things like old-tag which contain query metacharacters
         parts = program.split(':', 1)
         if all(lookup(sym) for sym in parts if sym):
             if parts[0]:
                 yield ('symbol', parts[0], 0)
             if len(parts) > 1:
                 s = len(parts[0])
                 yield (':', None, s)
                 if parts[1]:
                     yield ('symbol', parts[1], s + 1)
             yield ('end', None, len(program))
             return
 
     pos, l = 0, len(program)
     while pos < l:
         c = program[pos]
         if c.isspace(): # skip inter-token whitespace
             pass
         elif c == ':' and program[pos:pos + 2] == '::': # look ahead carefully
             yield ('::', None, pos)
             pos += 1 # skip ahead
         elif c == '.' and program[pos:pos + 2] == '..': # look ahead carefully
             yield ('..', None, pos)
             pos += 1 # skip ahead
         elif c == '#' and program[pos:pos + 2] == '##': # look ahead carefully
             yield ('##', None, pos)
             pos += 1 # skip ahead
         elif c in "():=,-|&+!~^%": # handle simple operators
             yield (c, None, pos)
         elif (c in '"\'' or c == 'r' and
               program[pos:pos + 2] in ("r'", 'r"')): # handle quoted strings
             if c == 'r':
                 pos += 1
                 c = program[pos]
                 decode = lambda x: x
             else:
                 decode = parser.unescapestr
             pos += 1
             s = pos
             while pos < l: # find closing quote
                 d = program[pos]
                 if d == '\\': # skip over escaped characters
                     pos += 2
                     continue
                 if d == c:
                     yield ('string', decode(program[s:pos]), s)
                     break
                 pos += 1
             else:
                 raise error.ParseError(_("unterminated string"), s)
         # gather up a symbol/keyword
         elif c in syminitletters:
             s = pos
             pos += 1
             while pos < l: # find end of symbol
                 d = program[pos]
                 if d not in symletters:
                     break
                 if d == '.' and program[pos - 1] == '.': # special case for ..
                     pos -= 1
                     break
                 pos += 1
             sym = program[s:pos]
             if sym in keywords: # operator keywords
                 yield (sym, None, s)
             elif '-' in sym:
                 # some jerk gave us foo-bar-baz, try to check if it's a symbol
                 if lookup and lookup(sym):
                     # looks like a real symbol
                     yield ('symbol', sym, s)
                 else:
                     # looks like an expression
                     parts = sym.split('-')
                     for p in parts[:-1]:
                         if p: # possible consecutive -
                             yield ('symbol', p, s)
                         s += len(p)
                         yield ('-', None, pos)
                         s += 1
                     if parts[-1]: # possible trailing -
                         yield ('symbol', parts[-1], s)
             else:
                 yield ('symbol', sym, s)
             pos -= 1
         else:
             raise error.ParseError(_("syntax error in revset '%s'") %
                                    program, pos)
         pos += 1
     yield ('end', None, pos)
 
 # helpers
 
 def getstring(x, err):
     if x and (x[0] == 'string' or x[0] == 'symbol'):
         return x[1]
     raise error.ParseError(err)
 
 def getlist(x):
     if not x:
         return []
     if x[0] == 'list':
         return list(x[1:])
     return [x]
 
 def getargs(x, min, max, err):
     l = getlist(x)
     if len(l) < min or (max >= 0 and len(l) > max):
         raise error.ParseError(err)
     return l
 
 def getargsdict(x, funcname, keys):
     return parser.buildargsdict(getlist(x), funcname, keys.split(),
                                 keyvaluenode='keyvalue', keynode='symbol')
 
 def getset(repo, subset, x):
     if not x:
         raise error.ParseError(_("missing argument"))
     s = methods[x[0]](repo, subset, *x[1:])
     if util.safehasattr(s, 'isascending'):
         return s
     if (repo.ui.configbool('devel', 'all-warnings')
             or repo.ui.configbool('devel', 'old-revset')):
         # else case should not happen, because all non-func are internal,
         # ignoring for now.
         if x[0] == 'func' and x[1][0] == 'symbol' and x[1][1] in symbols:
             repo.ui.develwarn('revset "%s" use list instead of smartset, '
                               '(upgrade your code)' % x[1][1])
     return baseset(s)
 
 def _getrevsource(repo, r):
     extra = repo[r].extra()
     for label in ('source', 'transplant_source', 'rebase_source'):
         if label in extra:
             try:
                 return repo[extra[label]].rev()
             except error.RepoLookupError:
                 pass
     return None
 
 # operator methods
 
 def stringset(repo, subset, x):
     x = repo[x].rev()
     if (x in subset
         or x == node.nullrev and isinstance(subset, fullreposet)):
         return baseset([x])
     return baseset()
 
 def rangeset(repo, subset, x, y):
     m = getset(repo, fullreposet(repo), x)
     n = getset(repo, fullreposet(repo), y)
 
     if not m or not n:
         return baseset()
     m, n = m.first(), n.last()
 
     if m == n:
         r = baseset([m])
     elif n == node.wdirrev:
         r = spanset(repo, m, len(repo)) + baseset([n])
     elif m == node.wdirrev:
         r = baseset([m]) + spanset(repo, len(repo) - 1, n - 1)
     elif m < n:
         r = spanset(repo, m, n + 1)
     else:
         r = spanset(repo, m, n - 1)
     # XXX We should combine with subset first: 'subset & baseset(...)'. This is
     # necessary to ensure we preserve the order in subset.
     #
     # This has performance implication, carrying the sorting over when possible
     # would be more efficient.
     return r & subset
 
 def dagrange(repo, subset, x, y):
     r = fullreposet(repo)
     xs = reachableroots(repo, getset(repo, r, x), getset(repo, r, y),
                          includepath=True)
     # XXX We should combine with subset first: 'subset & baseset(...)'. This is
     # necessary to ensure we preserve the order in subset.
     return xs & subset
 
 def andset(repo, subset, x, y):
     return getset(repo, getset(repo, subset, x), y)
 
 def differenceset(repo, subset, x, y):
     return getset(repo, subset, x) - getset(repo, subset, y)
 
 def orset(repo, subset, *xs):
     assert xs
     if len(xs) == 1:
         return getset(repo, subset, xs[0])
     p = len(xs) // 2
     a = orset(repo, subset, *xs[:p])
     b = orset(repo, subset, *xs[p:])
     return a + b
 
 def notset(repo, subset, x):
     return subset - getset(repo, subset, x)
 
 def listset(repo, subset, *xs):
     raise error.ParseError(_("can't use a list in this context"),
                            hint=_('see hg help "revsets.x or y"'))
 
 def keyvaluepair(repo, subset, k, v):
     raise error.ParseError(_("can't use a key-value pair in this context"))
 
 def func(repo, subset, a, b):
     if a[0] == 'symbol' and a[1] in symbols:
         return symbols[a[1]](repo, subset, b)
 
     keep = lambda fn: getattr(fn, '__doc__', None) is not None
 
     syms = [s for (s, fn) in symbols.items() if keep(fn)]
     raise error.UnknownIdentifier(a[1], syms)
 
 # functions
 
 # symbols are callables like:
 #   fn(repo, subset, x)
 # with:
 #   repo - current repository instance
 #   subset - of revisions to be examined
 #   x - argument in tree form
 symbols = {}
 
 # symbols which can't be used for a DoS attack for any given input
 # (e.g. those which accept regexes as plain strings shouldn't be included)
 # functions that just return a lot of changesets (like all) don't count here
 safesymbols = set()
 
 predicate = registrar.revsetpredicate()
 
 @predicate('_destupdate')
 def _destupdate(repo, subset, x):
     # experimental revset for update destination
     args = getargsdict(x, 'limit', 'clean check')
     return subset & baseset([destutil.destupdate(repo, **args)[0]])
 
 @predicate('_destmerge')
 def _destmerge(repo, subset, x):
     # experimental revset for merge destination
     sourceset = None
     if x is not None:
         sourceset = getset(repo, fullreposet(repo), x)
     return subset & baseset([destutil.destmerge(repo, sourceset=sourceset)])
 
 @predicate('adds(pattern)', safe=True)
 def adds(repo, subset, x):
     """Changesets that add a file matching pattern.
 
     The pattern without explicit kind like ``glob:`` is expected to be
     relative to the current directory and match against a file or a
     directory.
     """
     # i18n: "adds" is a keyword
     pat = getstring(x, _("adds requires a pattern"))
     return checkstatus(repo, subset, pat, 1)
 
 @predicate('ancestor(*changeset)', safe=True)
 def ancestor(repo, subset, x):
     """A greatest common ancestor of the changesets.
 
     Accepts 0 or more changesets.
     Will return empty list when passed no args.
     Greatest common ancestor of a single changeset is that changeset.
     """
     # i18n: "ancestor" is a keyword
     l = getlist(x)
     rl = fullreposet(repo)
     anc = None
 
     # (getset(repo, rl, i) for i in l) generates a list of lists
     for revs in (getset(repo, rl, i) for i in l):
         for r in revs:
             if anc is None:
                 anc = repo[r]
             else:
                 anc = anc.ancestor(repo[r])
 
     if anc is not None and anc.rev() in subset:
         return baseset([anc.rev()])
     return baseset()
 
 def _ancestors(repo, subset, x, followfirst=False):
     heads = getset(repo, fullreposet(repo), x)
     if not heads:
         return baseset()
     s = _revancestors(repo, heads, followfirst)
     return subset & s
 
 @predicate('ancestors(set)', safe=True)
 def ancestors(repo, subset, x):
     """Changesets that are ancestors of a changeset in set.
     """
     return _ancestors(repo, subset, x)
 
 @predicate('_firstancestors', safe=True)
 def _firstancestors(repo, subset, x):
     # ``_firstancestors(set)``
     # Like ``ancestors(set)`` but follows only the first parents.
     return _ancestors(repo, subset, x, followfirst=True)
 
 def ancestorspec(repo, subset, x, n):
     """``set~n``
     Changesets that are the Nth ancestor (first parents only) of a changeset
     in set.
     """
     try:
         n = int(n[1])
     except (TypeError, ValueError):
         raise error.ParseError(_("~ expects a number"))
     ps = set()
     cl = repo.changelog
     for r in getset(repo, fullreposet(repo), x):
         for i in range(n):
             r = cl.parentrevs(r)[0]
         ps.add(r)
     return subset & ps
 
 @predicate('author(string)', safe=True)
 def author(repo, subset, x):
     """Alias for ``user(string)``.
     """
     # i18n: "author" is a keyword
     n = encoding.lower(getstring(x, _("author requires a string")))
     kind, pattern, matcher = _substringmatcher(n)
     return subset.filter(lambda x: matcher(encoding.lower(repo[x].user())),
                          condrepr=('<user %r>', n))
 
 @predicate('bisect(string)', safe=True)
 def bisect(repo, subset, x):
     """Changesets marked in the specified bisect status:
 
     - ``good``, ``bad``, ``skip``: csets explicitly marked as good/bad/skip
     - ``goods``, ``bads``      : csets topologically good/bad
     - ``range``              : csets taking part in the bisection
     - ``pruned``             : csets that are goods, bads or skipped
     - ``untested``           : csets whose fate is yet unknown
     - ``ignored``            : csets ignored due to DAG topology
     - ``current``            : the cset currently being bisected
     """
     # i18n: "bisect" is a keyword
     status = getstring(x, _("bisect requires a string")).lower()
     state = set(hbisect.get(repo, status))
     return subset & state
 
 # Backward-compatibility
 # - no help entry so that we do not advertise it any more
 @predicate('bisected', safe=True)
 def bisected(repo, subset, x):
     return bisect(repo, subset, x)
 
 @predicate('bookmark([name])', safe=True)
 def bookmark(repo, subset, x):
     """The named bookmark or all bookmarks.
 
     If `name` starts with `re:`, the remainder of the name is treated as
     a regular expression. To match a bookmark that actually starts with `re:`,
     use the prefix `literal:`.
     """
     # i18n: "bookmark" is a keyword
     args = getargs(x, 0, 1, _('bookmark takes one or no arguments'))
     if args:
         bm = getstring(args[0],
                        # i18n: "bookmark" is a keyword
                        _('the argument to bookmark must be a string'))
         kind, pattern, matcher = util.stringmatcher(bm)
         bms = set()
         if kind == 'literal':
             bmrev = repo._bookmarks.get(pattern, None)
             if not bmrev:
                 raise error.RepoLookupError(_("bookmark '%s' does not exist")
                                             % pattern)
             bms.add(repo[bmrev].rev())
         else:
             matchrevs = set()
             for name, bmrev in repo._bookmarks.iteritems():
                 if matcher(name):
                     matchrevs.add(bmrev)
             if not matchrevs:
                 raise error.RepoLookupError(_("no bookmarks exist"
                                               " that match '%s'") % pattern)
             for bmrev in matchrevs:
                 bms.add(repo[bmrev].rev())
     else:
         bms = set([repo[r].rev()
                    for r in repo._bookmarks.values()])
     bms -= set([node.nullrev])
     return subset & bms
 
 @predicate('branch(string or set)', safe=True)
 def branch(repo, subset, x):
     """
     All changesets belonging to the given branch or the branches of the given
     changesets.
 
     If `string` starts with `re:`, the remainder of the name is treated as
     a regular expression. To match a branch that actually starts with `re:`,
     use the prefix `literal:`.
     """
     getbi = repo.revbranchcache().branchinfo
 
     try:
         b = getstring(x, '')
     except error.ParseError:
         # not a string, but another revspec, e.g. tip()
         pass
     else:
         kind, pattern, matcher = util.stringmatcher(b)
         if kind == 'literal':
             # note: falls through to the revspec case if no branch with
             # this name exists and pattern kind is not specified explicitly
             if pattern in repo.branchmap():
                 return subset.filter(lambda r: matcher(getbi(r)[0]),
                                      condrepr=('<branch %r>', b))
             if b.startswith('literal:'):
                 raise error.RepoLookupError(_("branch '%s' does not exist")
                                             % pattern)
         else:
             return subset.filter(lambda r: matcher(getbi(r)[0]),
                                  condrepr=('<branch %r>', b))
 
     s = getset(repo, fullreposet(repo), x)
     b = set()
     for r in s:
         b.add(getbi(r)[0])
     c = s.__contains__
     return subset.filter(lambda r: c(r) or getbi(r)[0] in b,
                          condrepr=lambda: '<branch %r>' % sorted(b))
 
 @predicate('bumped()', safe=True)
 def bumped(repo, subset, x):
     """Mutable changesets marked as successors of public changesets.
 
     Only non-public and non-obsolete changesets can be `bumped`.
     """
     # i18n: "bumped" is a keyword
     getargs(x, 0, 0, _("bumped takes no arguments"))
     bumped = obsmod.getrevs(repo, 'bumped')
     return subset & bumped
 
 @predicate('bundle()', safe=True)
 def bundle(repo, subset, x):
     """Changesets in the bundle.
 
     Bundle must be specified by the -R option."""
 
     try:
         bundlerevs = repo.changelog.bundlerevs
     except AttributeError:
         raise error.Abort(_("no bundle provided - specify with -R"))
     return subset & bundlerevs
 
 def checkstatus(repo, subset, pat, field):
     hasset = matchmod.patkind(pat) == 'set'
 
     mcache = [None]
     def matches(x):
         c = repo[x]
         if not mcache[0] or hasset:
             mcache[0] = matchmod.match(repo.root, repo.getcwd(), [pat], ctx=c)
         m = mcache[0]
         fname = None
         if not m.anypats() and len(m.files()) == 1:
             fname = m.files()[0]
         if fname is not None:
             if fname not in c.files():
                 return False
         else:
             for f in c.files():
                 if m(f):
                     break
             else:
                 return False
         files = repo.status(c.p1().node(), c.node())[field]
         if fname is not None:
             if fname in files:
                 return True
         else:
             for f in files:
                 if m(f):
                     return True
 
     return subset.filter(matches, condrepr=('<status[%r] %r>', field, pat))
 
 def _children(repo, narrow, parentset):
     if not parentset:
         return baseset()
     cs = set()
     pr = repo.changelog.parentrevs
     minrev = parentset.min()
     for r in narrow:
         if r <= minrev:
             continue
         for p in pr(r):
             if p in parentset:
                 cs.add(r)
     # XXX using a set to feed the baseset is wrong. Sets are not ordered.
     # This does not break because of other fullreposet misbehavior.
     return baseset(cs)
 
 @predicate('children(set)', safe=True)
 def children(repo, subset, x):
     """Child changesets of changesets in set.
     """
     s = getset(repo, fullreposet(repo), x)
     cs = _children(repo, subset, s)
     return subset & cs
 
 @predicate('closed()', safe=True)
 def closed(repo, subset, x):
     """Changeset is closed.
     """
     # i18n: "closed" is a keyword
     getargs(x, 0, 0, _("closed takes no arguments"))
     return subset.filter(lambda r: repo[r].closesbranch(),
                          condrepr='<branch closed>')
 
 @predicate('contains(pattern)')
 def contains(repo, subset, x):
     """The revision's manifest contains a file matching pattern (but might not
     modify it). See :hg:`help patterns` for information about file patterns.
 
     The pattern without explicit kind like ``glob:`` is expected to be
     relative to the current directory and match against a file exactly
     for efficiency.
     """
     # i18n: "contains" is a keyword
     pat = getstring(x, _("contains requires a pattern"))
 
     def matches(x):
         if not matchmod.patkind(pat):
             pats = pathutil.canonpath(repo.root, repo.getcwd(), pat)
             if pats in repo[x]:
                 return True
         else:
             c = repo[x]
             m = matchmod.match(repo.root, repo.getcwd(), [pat], ctx=c)
             for f in c.manifest():
                 if m(f):
                     return True
         return False
 
     return subset.filter(matches, condrepr=('<contains %r>', pat))
 
 @predicate('converted([id])', safe=True)
 def converted(repo, subset, x):
     """Changesets converted from the given identifier in the old repository if
     present, or all converted changesets if no identifier is specified.
     """
 
     # There is exactly no chance of resolving the revision, so do a simple
     # string compare and hope for the best
 
     rev = None
     # i18n: "converted" is a keyword
     l = getargs(x, 0, 1, _('converted takes one or no arguments'))
     if l:
         # i18n: "converted" is a keyword
         rev = getstring(l[0], _('converted requires a revision'))
 
     def _matchvalue(r):
         source = repo[r].extra().get('convert_revision', None)
         return source is not None and (rev is None or source.startswith(rev))
 
     return subset.filter(lambda r: _matchvalue(r),
                          condrepr=('<converted %r>', rev))
 
 @predicate('date(interval)', safe=True)
 def date(repo, subset, x):
     """Changesets within the interval, see :hg:`help dates`.
     """
     # i18n: "date" is a keyword
     ds = getstring(x, _("date requires a string"))
     dm = util.matchdate(ds)
     return subset.filter(lambda x: dm(repo[x].date()[0]),
                          condrepr=('<date %r>', ds))
 
 @predicate('desc(string)', safe=True)
 def desc(repo, subset, x):
     """Search commit message for string. The match is case-insensitive.
     """
     # i18n: "desc" is a keyword
     ds = encoding.lower(getstring(x, _("desc requires a string")))
 
     def matches(x):
         c = repo[x]
         return ds in encoding.lower(c.description())
 
     return subset.filter(matches, condrepr=('<desc %r>', ds))
 
 def _descendants(repo, subset, x, followfirst=False):
     roots = getset(repo, fullreposet(repo), x)
     if not roots:
         return baseset()
     s = _revdescendants(repo, roots, followfirst)
 
     # Both sets need to be ascending in order to lazily return the union
     # in the correct order.
     base = subset & roots
     desc = subset & s
     result = base + desc
     if subset.isascending():
         result.sort()
     elif subset.isdescending():
         result.sort(reverse=True)
     else:
         result = subset & result
     return result
 
 @predicate('descendants(set)', safe=True)
 def descendants(repo, subset, x):
     """Changesets which are descendants of changesets in set.
     """
     return _descendants(repo, subset, x)
 
 @predicate('_firstdescendants', safe=True)
 def _firstdescendants(repo, subset, x):
     # ``_firstdescendants(set)``
     # Like ``descendants(set)`` but follows only the first parents.
     return _descendants(repo, subset, x, followfirst=True)
 
 @predicate('destination([set])', safe=True)
 def destination(repo, subset, x):
     """Changesets that were created by a graft, transplant or rebase operation,
     with the given revisions specified as the source.  Omitting the optional set
     is the same as passing all().
     """
     if x is not None:
         sources = getset(repo, fullreposet(repo), x)
     else:
         sources = fullreposet(repo)
 
     dests = set()
 
     # subset contains all of the possible destinations that can be returned, so
     # iterate over them and see if their source(s) were provided in the arg set.
     # Even if the immediate src of r is not in the arg set, src's source (or
     # further back) may be.  Scanning back further than the immediate src allows
     # transitive transplants and rebases to yield the same results as transitive
     # grafts.
     for r in subset:
         src = _getrevsource(repo, r)
         lineage = None
 
         while src is not None:
             if lineage is None:
                 lineage = list()
 
             lineage.append(r)
 
             # The visited lineage is a match if the current source is in the arg
             # set.  Since every candidate dest is visited by way of iterating
             # subset, any dests further back in the lineage will be tested by a
             # different iteration over subset.  Likewise, if the src was already
             # selected, the current lineage can be selected without going back
             # further.
             if src in sources or src in dests:
                 dests.update(lineage)
                 break
 
             r = src
             src = _getrevsource(repo, r)
 
     return subset.filter(dests.__contains__,
                          condrepr=lambda: '<destination %r>' % sorted(dests))
 
 @predicate('divergent()', safe=True)
 def divergent(repo, subset, x):
     """
     Final successors of changesets with an alternative set of final successors.
     """
     # i18n: "divergent" is a keyword
     getargs(x, 0, 0, _("divergent takes no arguments"))
     divergent = obsmod.getrevs(repo, 'divergent')
     return subset & divergent
 
 @predicate('extinct()', safe=True)
 def extinct(repo, subset, x):
     """Obsolete changesets with obsolete descendants only.
     """
     # i18n: "extinct" is a keyword
     getargs(x, 0, 0, _("extinct takes no arguments"))
     extincts = obsmod.getrevs(repo, 'extinct')
     return subset & extincts
 
 @predicate('extra(label, [value])', safe=True)
 def extra(repo, subset, x):
     """Changesets with the given label in the extra metadata, with the given
     optional value.
 
     If `value` starts with `re:`, the remainder of the value is treated as
     a regular expression. To match a value that actually starts with `re:`,
     use the prefix `literal:`.
     """
     args = getargsdict(x, 'extra', 'label value')
     if 'label' not in args:
         # i18n: "extra" is a keyword
         raise error.ParseError(_('extra takes at least 1 argument'))
     # i18n: "extra" is a keyword
     label = getstring(args['label'], _('first argument to extra must be '
                                        'a string'))
     value = None
 
     if 'value' in args:
         # i18n: "extra" is a keyword
         value = getstring(args['value'], _('second argument to extra must be '
                                            'a string'))
         kind, value, matcher = util.stringmatcher(value)
 
     def _matchvalue(r):
         extra = repo[r].extra()
         return label in extra and (value is None or matcher(extra[label]))
 
     return subset.filter(lambda r: _matchvalue(r),
                          condrepr=('<extra[%r] %r>', label, value))
 
 @predicate('filelog(pattern)', safe=True)
 def filelog(repo, subset, x):
     """Changesets connected to the specified filelog.
 
     For performance reasons, visits only revisions mentioned in the file-level
     filelog, rather than filtering through all changesets (much faster, but
     doesn't include deletes or duplicate changes). For a slower, more accurate
     result, use ``file()``.
 
     The pattern without explicit kind like ``glob:`` is expected to be
     relative to the current directory and match against a file exactly
     for efficiency.
 
     If some linkrev points to revisions filtered by the current repoview, we'll
     work around it to return a non-filtered value.
     """
 
     # i18n: "filelog" is a keyword
     pat = getstring(x, _("filelog requires a pattern"))
     s = set()
     cl = repo.changelog
 
     if not matchmod.patkind(pat):
         f = pathutil.canonpath(repo.root, repo.getcwd(), pat)
         files = [f]
     else:
         m = matchmod.match(repo.root, repo.getcwd(), [pat], ctx=repo[None])
         files = (f for f in repo[None] if m(f))
 
     for f in files:
         fl = repo.file(f)
         known = {}
         scanpos = 0
         for fr in list(fl):
             fn = fl.node(fr)
             if fn in known:
                 s.add(known[fn])
                 continue
 
             lr = fl.linkrev(fr)
             if lr in cl:
                 s.add(lr)
             elif scanpos is not None:
                 # lowest matching changeset is filtered, scan further
                 # ahead in changelog
                 start = max(lr, scanpos) + 1
                 scanpos = None
                 for r in cl.revs(start):
                     # minimize parsing of non-matching entries
                     if f in cl.revision(r) and f in cl.readfiles(r):
                         try:
                             # try to use manifest delta fastpath
                             n = repo[r].filenode(f)
                             if n not in known:
                                 if n == fn:
                                     s.add(r)
                                     scanpos = r
                                     break
                                 else:
                                     known[n] = r
                         except error.ManifestLookupError:
                             # deletion in changelog
                             continue
 
     return subset & s
 
 @predicate('first(set, [n])', safe=True)
 def first(repo, subset, x):
     """An alias for limit().
     """
     return limit(repo, subset, x)
 
 def _follow(repo, subset, x, name, followfirst=False):
     l = getargs(x, 0, 1, _("%s takes no arguments or a pattern") % name)
     c = repo['.']
     if l:
         x = getstring(l[0], _("%s expected a pattern") % name)
         matcher = matchmod.match(repo.root, repo.getcwd(), [x],
                                  ctx=repo[None], default='path')
 
         files = c.manifest().walk(matcher)
 
         s = set()
         for fname in files:
             fctx = c[fname]
             s = s.union(set(c.rev() for c in fctx.ancestors(followfirst)))
             # include the revision responsible for the most recent version
             s.add(fctx.introrev())
     else:
         s = _revancestors(repo, baseset([c.rev()]), followfirst)
 
     return subset & s
 
 @predicate('follow([pattern])', safe=True)
 def follow(repo, subset, x):
     """
     An alias for ``::.`` (ancestors of the working directory's first parent).
     If pattern is specified, the histories of files matching given
     pattern is followed, including copies.
     """
     return _follow(repo, subset, x, 'follow')
 
 @predicate('_followfirst', safe=True)
 def _followfirst(repo, subset, x):
     # ``followfirst([pattern])``
     # Like ``follow([pattern])`` but follows only the first parent of
     # every revisions or files revisions.
     return _follow(repo, subset, x, '_followfirst', followfirst=True)
 
 @predicate('all()', safe=True)
 def getall(repo, subset, x):
     """All changesets, the same as ``0:tip``.
     """
     # i18n: "all" is a keyword
     getargs(x, 0, 0, _("all takes no arguments"))
     return subset & spanset(repo)  # drop "null" if any
 
 @predicate('grep(regex)')
 def grep(repo, subset, x):
     """Like ``keyword(string)`` but accepts a regex. Use ``grep(r'...')``
     to ensure special escape characters are handled correctly. Unlike
     ``keyword(string)``, the match is case-sensitive.
     """
     try:
         # i18n: "grep" is a keyword
         gr = re.compile(getstring(x, _("grep requires a string")))
     except re.error as e:
         raise error.ParseError(_('invalid match pattern: %s') % e)
 
     def matches(x):
         c = repo[x]
         for e in c.files() + [c.user(), c.description()]:
             if gr.search(e):
                 return True
         return False
 
     return subset.filter(matches, condrepr=('<grep %r>', gr.pattern))
 
 @predicate('_matchfiles', safe=True)
 def _matchfiles(repo, subset, x):
     # _matchfiles takes a revset list of prefixed arguments:
     #
     #   [p:foo, i:bar, x:baz]
     #
     # builds a match object from them and filters subset. Allowed
     # prefixes are 'p:' for regular patterns, 'i:' for include
     # patterns and 'x:' for exclude patterns. Use 'r:' prefix to pass
     # a revision identifier, or the empty string to reference the
     # working directory, from which the match object is
     # initialized. Use 'd:' to set the default matching mode, default
     # to 'glob'. At most one 'r:' and 'd:' argument can be passed.
 
     l = getargs(x, 1, -1, "_matchfiles requires at least one argument")
     pats, inc, exc = [], [], []
     rev, default = None, None
     for arg in l:
         s = getstring(arg, "_matchfiles requires string arguments")
         prefix, value = s[:2], s[2:]
         if prefix == 'p:':
             pats.append(value)
         elif prefix == 'i:':
             inc.append(value)
         elif prefix == 'x:':
             exc.append(value)
         elif prefix == 'r:':
             if rev is not None:
                 raise error.ParseError('_matchfiles expected at most one '
                                        'revision')
             if value != '': # empty means working directory; leave rev as None
                 rev = value
         elif prefix == 'd:':
             if default is not None:
                 raise error.ParseError('_matchfiles expected at most one '
                                        'default mode')
             default = value
         else:
             raise error.ParseError('invalid _matchfiles prefix: %s' % prefix)
     if not default:
         default = 'glob'
 
     m = matchmod.match(repo.root, repo.getcwd(), pats, include=inc,
                        exclude=exc, ctx=repo[rev], default=default)
 
     # This directly read the changelog data as creating changectx for all
     # revisions is quite expensive.
     getfiles = repo.changelog.readfiles
     wdirrev = node.wdirrev
     def matches(x):
         if x == wdirrev:
             files = repo[x].files()
         else:
             files = getfiles(x)
         for f in files:
             if m(f):
                 return True
         return False
 
     return subset.filter(matches,
                          condrepr=('<matchfiles patterns=%r, include=%r '
                                    'exclude=%r, default=%r, rev=%r>',
                                    pats, inc, exc, default, rev))
 
 @predicate('file(pattern)', safe=True)
 def hasfile(repo, subset, x):
     """Changesets affecting files matched by pattern.
 
     For a faster but less accurate result, consider using ``filelog()``
     instead.
 
     This predicate uses ``glob:`` as the default kind of pattern.
     """
     # i18n: "file" is a keyword
     pat = getstring(x, _("file requires a pattern"))
     return _matchfiles(repo, subset, ('string', 'p:' + pat))
 
 @predicate('head()', safe=True)
 def head(repo, subset, x):
     """Changeset is a named branch head.
     """
     # i18n: "head" is a keyword
     getargs(x, 0, 0, _("head takes no arguments"))
     hs = set()
     cl = repo.changelog
     for b, ls in repo.branchmap().iteritems():
         hs.update(cl.rev(h) for h in ls)
     # XXX using a set to feed the baseset is wrong. Sets are not ordered.
     # This does not break because of other fullreposet misbehavior.
     # XXX We should combine with subset first: 'subset & baseset(...)'. This is
     # necessary to ensure we preserve the order in subset.
     return baseset(hs) & subset
 
 @predicate('heads(set)', safe=True)
 def heads(repo, subset, x):
     """Members of set with no children in set.
     """
     s = getset(repo, subset, x)
     ps = parents(repo, subset, x)
     return s - ps
 
 @predicate('hidden()', safe=True)
 def hidden(repo, subset, x):
     """Hidden changesets.
     """
     # i18n: "hidden" is a keyword
     getargs(x, 0, 0, _("hidden takes no arguments"))
     hiddenrevs = repoview.filterrevs(repo, 'visible')
     return subset & hiddenrevs
 
 @predicate('keyword(string)', safe=True)
 def keyword(repo, subset, x):
     """Search commit message, user name, and names of changed files for
     string. The match is case-insensitive.
     """
     # i18n: "keyword" is a keyword
     kw = encoding.lower(getstring(x, _("keyword requires a string")))
 
     def matches(r):
         c = repo[r]
         return any(kw in encoding.lower(t)
                    for t in c.files() + [c.user(), c.description()])
 
     return subset.filter(matches, condrepr=('<keyword %r>', kw))
 
 @predicate('limit(set[, n[, offset]])', safe=True)
 def limit(repo, subset, x):
     """First n members of set, defaulting to 1, starting from offset.
     """
     args = getargsdict(x, 'limit', 'set n offset')
     if 'set' not in args:
         # i18n: "limit" is a keyword
         raise error.ParseError(_("limit requires one to three arguments"))
     try:
         lim, ofs = 1, 0
         if 'n' in args:
             # i18n: "limit" is a keyword
             lim = int(getstring(args['n'], _("limit requires a number")))
         if 'offset' in args:
             # i18n: "limit" is a keyword
             ofs = int(getstring(args['offset'], _("limit requires a number")))
         if ofs < 0:
             raise error.ParseError(_("negative offset"))
     except (TypeError, ValueError):
         # i18n: "limit" is a keyword
         raise error.ParseError(_("limit expects a number"))
     os = getset(repo, fullreposet(repo), args['set'])
     result = []
     it = iter(os)
     for x in xrange(ofs):
         y = next(it, None)
         if y is None:
             break
     for x in xrange(lim):
         y = next(it, None)
         if y is None:
             break
         elif y in subset:
             result.append(y)
     return baseset(result, datarepr=('<limit n=%d, offset=%d, %r, %r>',
                                      lim, ofs, subset, os))
 
 @predicate('last(set, [n])', safe=True)
 def last(repo, subset, x):
     """Last n members of set, defaulting to 1.
     """
     # i18n: "last" is a keyword
     l = getargs(x, 1, 2, _("last requires one or two arguments"))
     try:
         lim = 1
         if len(l) == 2:
             # i18n: "last" is a keyword
             lim = int(getstring(l[1], _("last requires a number")))
     except (TypeError, ValueError):
         # i18n: "last" is a keyword
         raise error.ParseError(_("last expects a number"))
     os = getset(repo, fullreposet(repo), l[0])
     os.reverse()
     result = []
     it = iter(os)
     for x in xrange(lim):
         y = next(it, None)
         if y is None:
             break
         elif y in subset:
             result.append(y)
     return baseset(result, datarepr=('<last n=%d, %r, %r>', lim, subset, os))
 
 @predicate('max(set)', safe=True)
 def maxrev(repo, subset, x):
     """Changeset with highest revision number in set.
     """
     os = getset(repo, fullreposet(repo), x)
     try:
         m = os.max()
         if m in subset:
             return baseset([m], datarepr=('<max %r, %r>', subset, os))
     except ValueError:
         # os.max() throws a ValueError when the collection is empty.
         # Same as python's max().
         pass
     return baseset(datarepr=('<max %r, %r>', subset, os))
 
 @predicate('merge()', safe=True)
 def merge(repo, subset, x):
     """Changeset is a merge changeset.
     """
     # i18n: "merge" is a keyword
     getargs(x, 0, 0, _("merge takes no arguments"))
     cl = repo.changelog
     return subset.filter(lambda r: cl.parentrevs(r)[1] != -1,
                          condrepr='<merge>')
 
 @predicate('branchpoint()', safe=True)
 def branchpoint(repo, subset, x):
     """Changesets with more than one child.
     """
     # i18n: "branchpoint" is a keyword
     getargs(x, 0, 0, _("branchpoint takes no arguments"))
     cl = repo.changelog
     if not subset:
         return baseset()
     # XXX this should be 'parentset.min()' assuming 'parentset' is a smartset
     # (and if it is not, it should.)
     baserev = min(subset)
     parentscount = [0]*(len(repo) - baserev)
     for r in cl.revs(start=baserev + 1):
         for p in cl.parentrevs(r):
             if p >= baserev:
                 parentscount[p - baserev] += 1
     return subset.filter(lambda r: parentscount[r - baserev] > 1,
                          condrepr='<branchpoint>')
 
 @predicate('min(set)', safe=True)
 def minrev(repo, subset, x):
     """Changeset with lowest revision number in set.
     """
     os = getset(repo, fullreposet(repo), x)
     try:
         m = os.min()
         if m in subset:
             return baseset([m], datarepr=('<min %r, %r>', subset, os))
     except ValueError:
         # os.min() throws a ValueError when the collection is empty.
         # Same as python's min().
         pass
     return baseset(datarepr=('<min %r, %r>', subset, os))
 
 @predicate('modifies(pattern)', safe=True)
 def modifies(repo, subset, x):
     """Changesets modifying files matched by pattern.
 
     The pattern without explicit kind like ``glob:`` is expected to be
     relative to the current directory and match against a file or a
     directory.
     """
     # i18n: "modifies" is a keyword
     pat = getstring(x, _("modifies requires a pattern"))
     return checkstatus(repo, subset, pat, 0)
 
 @predicate('named(namespace)')
 def named(repo, subset, x):
     """The changesets in a given namespace.
 
     If `namespace` starts with `re:`, the remainder of the string is treated as
     a regular expression. To match a namespace that actually starts with `re:`,
     use the prefix `literal:`.
     """
     # i18n: "named" is a keyword
     args = getargs(x, 1, 1, _('named requires a namespace argument'))
 
     ns = getstring(args[0],
                    # i18n: "named" is a keyword
                    _('the argument to named must be a string'))
     kind, pattern, matcher = util.stringmatcher(ns)
     namespaces = set()
     if kind == 'literal':
         if pattern not in repo.names:
             raise error.RepoLookupError(_("namespace '%s' does not exist")
                                         % ns)
         namespaces.add(repo.names[pattern])
     else:
         for name, ns in repo.names.iteritems():
             if matcher(name):
                 namespaces.add(ns)
         if not namespaces:
             raise error.RepoLookupError(_("no namespace exists"
                                           " that match '%s'") % pattern)
 
     names = set()
     for ns in namespaces:
         for name in ns.listnames(repo):
             if name not in ns.deprecated:
                 names.update(repo[n].rev() for n in ns.nodes(repo, name))
 
     names -= set([node.nullrev])
     return subset & names
 
 @predicate('id(string)', safe=True)
 def node_(repo, subset, x):
     """Revision non-ambiguously specified by the given hex string prefix.
     """
     # i18n: "id" is a keyword
     l = getargs(x, 1, 1, _("id requires one argument"))
     # i18n: "id" is a keyword
     n = getstring(l[0], _("id requires a string"))
     if len(n) == 40:
         try:
             rn = repo.changelog.rev(node.bin(n))
         except (LookupError, TypeError):
             rn = None
     else:
         rn = None
         pm = repo.changelog._partialmatch(n)
         if pm is not None:
             rn = repo.changelog.rev(pm)
 
     if rn is None:
         return baseset()
     result = baseset([rn])
     return result & subset
 
 @predicate('obsolete()', safe=True)
 def obsolete(repo, subset, x):
     """Mutable changeset with a newer version."""
     # i18n: "obsolete" is a keyword
     getargs(x, 0, 0, _("obsolete takes no arguments"))
     obsoletes = obsmod.getrevs(repo, 'obsolete')
     return subset & obsoletes
 
 @predicate('only(set, [set])', safe=True)
 def only(repo, subset, x):
     """Changesets that are ancestors of the first set that are not ancestors
     of any other head in the repo. If a second set is specified, the result
     is ancestors of the first set that are not ancestors of the second set
     (i.e. ::<set1> - ::<set2>).
     """
     cl = repo.changelog
     # i18n: "only" is a keyword
     args = getargs(x, 1, 2, _('only takes one or two arguments'))
     include = getset(repo, fullreposet(repo), args[0])
     if len(args) == 1:
         if not include:
             return baseset()
 
         descendants = set(_revdescendants(repo, include, False))
         exclude = [rev for rev in cl.headrevs()
             if not rev in descendants and not rev in include]
     else:
         exclude = getset(repo, fullreposet(repo), args[1])
 
     results = set(cl.findmissingrevs(common=exclude, heads=include))
     # XXX we should turn this into a baseset instead of a set, smartset may do
     # some optimisations from the fact this is a baseset.
     return subset & results
 
 @predicate('origin([set])', safe=True)
 def origin(repo, subset, x):
     """
     Changesets that were specified as a source for the grafts, transplants or
     rebases that created the given revisions.  Omitting the optional set is the
     same as passing all().  If a changeset created by these operations is itself
     specified as a source for one of these operations, only the source changeset
     for the first operation is selected.
     """
     if x is not None:
         dests = getset(repo, fullreposet(repo), x)
     else:
         dests = fullreposet(repo)
 
     def _firstsrc(rev):
         src = _getrevsource(repo, rev)
         if src is None:
             return None
 
         while True:
             prev = _getrevsource(repo, src)
 
             if prev is None:
                 return src
             src = prev
 
     o = set([_firstsrc(r) for r in dests])
     o -= set([None])
     # XXX we should turn this into a baseset instead of a set, smartset may do
     # some optimisations from the fact this is a baseset.
     return subset & o
 
 @predicate('outgoing([path])', safe=True)
 def outgoing(repo, subset, x):
     """Changesets not found in the specified destination repository, or the
     default push location.
     """
     # Avoid cycles.
     from . import (
         discovery,
         hg,
     )
     # i18n: "outgoing" is a keyword
     l = getargs(x, 0, 1, _("outgoing takes one or no arguments"))
     # i18n: "outgoing" is a keyword
     dest = l and getstring(l[0], _("outgoing requires a repository path")) or ''
     dest = repo.ui.expandpath(dest or 'default-push', dest or 'default')
     dest, branches = hg.parseurl(dest)
     revs, checkout = hg.addbranchrevs(repo, repo, branches, [])
     if revs:
         revs = [repo.lookup(rev) for rev in revs]
     other = hg.peer(repo, {}, dest)
     repo.ui.pushbuffer()
     outgoing = discovery.findcommonoutgoing(repo, other, onlyheads=revs)
     repo.ui.popbuffer()
     cl = repo.changelog
     o = set([cl.rev(r) for r in outgoing.missing])
     return subset & o
 
 @predicate('p1([set])', safe=True)
 def p1(repo, subset, x):
     """First parent of changesets in set, or the working directory.
     """
     if x is None:
         p = repo[x].p1().rev()
         if p >= 0:
             return subset & baseset([p])
         return baseset()
 
     ps = set()
     cl = repo.changelog
     for r in getset(repo, fullreposet(repo), x):
         ps.add(cl.parentrevs(r)[0])
     ps -= set([node.nullrev])
     # XXX we should turn this into a baseset instead of a set, smartset may do
     # some optimisations from the fact this is a baseset.
     return subset & ps
 
 @predicate('p2([set])', safe=True)
 def p2(repo, subset, x):
     """Second parent of changesets in set, or the working directory.
     """
     if x is None:
         ps = repo[x].parents()
         try:
             p = ps[1].rev()
             if p >= 0:
                 return subset & baseset([p])
             return baseset()
         except IndexError:
             return baseset()
 
     ps = set()
     cl = repo.changelog
     for r in getset(repo, fullreposet(repo), x):
         ps.add(cl.parentrevs(r)[1])
     ps -= set([node.nullrev])
     # XXX we should turn this into a baseset instead of a set, smartset may do
     # some optimisations from the fact this is a baseset.
     return subset & ps
 
 @predicate('parents([set])', safe=True)
 def parents(repo, subset, x):
     """
     The set of all parents for all changesets in set, or the working directory.
     """
     if x is None:
         ps = set(p.rev() for p in repo[x].parents())
     else:
         ps = set()
         cl = repo.changelog
         up = ps.update
         parentrevs = cl.parentrevs
         for r in getset(repo, fullreposet(repo), x):
             if r == node.wdirrev:
                 up(p.rev() for p in repo[r].parents())
             else:
                 up(parentrevs(r))
     ps -= set([node.nullrev])
     return subset & ps
 
 def _phase(repo, subset, target):
     """helper to select all rev in phase <target>"""
     repo._phasecache.loadphaserevs(repo) # ensure phase's sets are loaded
     if repo._phasecache._phasesets:
         s = repo._phasecache._phasesets[target] - repo.changelog.filteredrevs
         s = baseset(s)
         s.sort() # set are non ordered, so we enforce ascending
         return subset & s
     else:
         phase = repo._phasecache.phase
         condition = lambda r: phase(repo, r) == target
         return subset.filter(condition, condrepr=('<phase %r>', target),
                              cache=False)
 
 @predicate('draft()', safe=True)
 def draft(repo, subset, x):
     """Changeset in draft phase."""
     # i18n: "draft" is a keyword
     getargs(x, 0, 0, _("draft takes no arguments"))
     target = phases.draft
     return _phase(repo, subset, target)
 
 @predicate('secret()', safe=True)
 def secret(repo, subset, x):
     """Changeset in secret phase."""
     # i18n: "secret" is a keyword
     getargs(x, 0, 0, _("secret takes no arguments"))
     target = phases.secret
     return _phase(repo, subset, target)
 
 def parentspec(repo, subset, x, n):
     """``set^0``
     The set.
     ``set^1`` (or ``set^``), ``set^2``
     First or second parent, respectively, of all changesets in set.
     """
     try:
         n = int(n[1])
         if n not in (0, 1, 2):
             raise ValueError
     except (TypeError, ValueError):
         raise error.ParseError(_("^ expects a number 0, 1, or 2"))
     ps = set()
     cl = repo.changelog
     for r in getset(repo, fullreposet(repo), x):
         if n == 0:
             ps.add(r)
         elif n == 1:
             ps.add(cl.parentrevs(r)[0])
         elif n == 2:
             parents = cl.parentrevs(r)
             if len(parents) > 1:
                 ps.add(parents[1])
     return subset & ps
 
 @predicate('present(set)', safe=True)
 def present(repo, subset, x):
     """An empty set, if any revision in set isn't found; otherwise,
     all revisions in set.
 
     If any of specified revisions is not present in the local repository,
     the query is normally aborted. But this predicate allows the query
     to continue even in such cases.
     """
     try:
         return getset(repo, subset, x)
     except error.RepoLookupError:
         return baseset()
 
 # for internal use
 @predicate('_notpublic', safe=True)
 def _notpublic(repo, subset, x):
     getargs(x, 0, 0, "_notpublic takes no arguments")
     repo._phasecache.loadphaserevs(repo) # ensure phase's sets are loaded
     if repo._phasecache._phasesets:
         s = set()
         for u in repo._phasecache._phasesets[1:]:
             s.update(u)
         s = baseset(s - repo.changelog.filteredrevs)
         s.sort()
         return subset & s
     else:
         phase = repo._phasecache.phase
         target = phases.public
         condition = lambda r: phase(repo, r) != target
         return subset.filter(condition, condrepr=('<phase %r>', target),
                              cache=False)
 
 @predicate('public()', safe=True)
 def public(repo, subset, x):
     """Changeset in public phase."""
     # i18n: "public" is a keyword
     getargs(x, 0, 0, _("public takes no arguments"))
     phase = repo._phasecache.phase
     target = phases.public
     condition = lambda r: phase(repo, r) == target
     return subset.filter(condition, condrepr=('<phase %r>', target),
                          cache=False)
 
 @predicate('remote([id [,path]])', safe=True)
 def remote(repo, subset, x):
     """Local revision that corresponds to the given identifier in a
     remote repository, if present. Here, the '.' identifier is a
     synonym for the current local branch.
     """
 
     from . import hg # avoid start-up nasties
     # i18n: "remote" is a keyword
     l = getargs(x, 0, 2, _("remote takes zero, one, or two arguments"))
 
     q = '.'
     if len(l) > 0:
     # i18n: "remote" is a keyword
         q = getstring(l[0], _("remote requires a string id"))
     if q == '.':
         q = repo['.'].branch()
 
     dest = ''
     if len(l) > 1:
         # i18n: "remote" is a keyword
         dest = getstring(l[1], _("remote requires a repository path"))
     dest = repo.ui.expandpath(dest or 'default')
     dest, branches = hg.parseurl(dest)
     revs, checkout = hg.addbranchrevs(repo, repo, branches, [])
     if revs:
         revs = [repo.lookup(rev) for rev in revs]
     other = hg.peer(repo, {}, dest)
     n = other.lookup(q)
     if n in repo:
         r = repo[n].rev()
         if r in subset:
             return baseset([r])
     return baseset()
 
 @predicate('removes(pattern)', safe=True)
 def removes(repo, subset, x):
     """Changesets which remove files matching pattern.
 
     The pattern without explicit kind like ``glob:`` is expected to be
     relative to the current directory and match against a file or a
     directory.
     """
     # i18n: "removes" is a keyword
     pat = getstring(x, _("removes requires a pattern"))
     return checkstatus(repo, subset, pat, 2)
 
 @predicate('rev(number)', safe=True)
 def rev(repo, subset, x):
     """Revision with the given numeric identifier.
     """
     # i18n: "rev" is a keyword
     l = getargs(x, 1, 1, _("rev requires one argument"))
     try:
         # i18n: "rev" is a keyword
         l = int(getstring(l[0], _("rev requires a number")))
     except (TypeError, ValueError):
         # i18n: "rev" is a keyword
         raise error.ParseError(_("rev expects a number"))
     if l not in repo.changelog and l != node.nullrev:
         return baseset()
     return subset & baseset([l])
 
 @predicate('matching(revision [, field])', safe=True)
 def matching(repo, subset, x):
     """Changesets in which a given set of fields match the set of fields in the
     selected revision or set.
 
     To match more than one field pass the list of fields to match separated
     by spaces (e.g. ``author description``).
 
     Valid fields are most regular revision fields and some special fields.
 
     Regular revision fields are ``description``, ``author``, ``branch``,
     ``date``, ``files``, ``phase``, ``parents``, ``substate``, ``user``
     and ``diff``.
     Note that ``author`` and ``user`` are synonyms. ``diff`` refers to the
     contents of the revision. Two revisions matching their ``diff`` will
     also match their ``files``.
 
     Special fields are ``summary`` and ``metadata``:
     ``summary`` matches the first line of the description.
     ``metadata`` is equivalent to matching ``description user date``
     (i.e. it matches the main metadata fields).
 
     ``metadata`` is the default field which is used when no fields are
     specified. You can match more than one field at a time.
     """
     # i18n: "matching" is a keyword
     l = getargs(x, 1, 2, _("matching takes 1 or 2 arguments"))
 
     revs = getset(repo, fullreposet(repo), l[0])
 
     fieldlist = ['metadata']
     if len(l) > 1:
             fieldlist = getstring(l[1],
                 # i18n: "matching" is a keyword
                 _("matching requires a string "
                 "as its second argument")).split()
 
     # Make sure that there are no repeated fields,
     # expand the 'special' 'metadata' field type
     # and check the 'files' whenever we check the 'diff'
     fields = []
     for field in fieldlist:
         if field == 'metadata':
             fields += ['user', 'description', 'date']
         elif field == 'diff':
             # a revision matching the diff must also match the files
             # since matching the diff is very costly, make sure to
             # also match the files first
             fields += ['files', 'diff']
         else:
             if field == 'author':
                 field = 'user'
             fields.append(field)
     fields = set(fields)
     if 'summary' in fields and 'description' in fields:
         # If a revision matches its description it also matches its summary
         fields.discard('summary')
 
     # We may want to match more than one field
     # Not all fields take the same amount of time to be matched
     # Sort the selected fields in order of increasing matching cost
     fieldorder = ['phase', 'parents', 'user', 'date', 'branch', 'summary',
         'files', 'description', 'substate', 'diff']
     def fieldkeyfunc(f):
         try:
             return fieldorder.index(f)
         except ValueError:
             # assume an unknown field is very costly
             return len(fieldorder)
     fields = list(fields)
     fields.sort(key=fieldkeyfunc)
 
     # Each field will be matched with its own "getfield" function
     # which will be added to the getfieldfuncs array of functions
     getfieldfuncs = []
     _funcs = {
         'user': lambda r: repo[r].user(),
         'branch': lambda r: repo[r].branch(),
         'date': lambda r: repo[r].date(),
         'description': lambda r: repo[r].description(),
         'files': lambda r: repo[r].files(),
         'parents': lambda r: repo[r].parents(),
         'phase': lambda r: repo[r].phase(),
         'substate': lambda r: repo[r].substate,
         'summary': lambda r: repo[r].description().splitlines()[0],
         'diff': lambda r: list(repo[r].diff(git=True),)
     }
     for info in fields:
         getfield = _funcs.get(info, None)
         if getfield is None:
             raise error.ParseError(
                 # i18n: "matching" is a keyword
                 _("unexpected field name passed to matching: %s") % info)
         getfieldfuncs.append(getfield)
     # convert the getfield array of functions into a "getinfo" function
     # which returns an array of field values (or a single value if there
     # is only one field to match)
     getinfo = lambda r: [f(r) for f in getfieldfuncs]
 
     def matches(x):
         for rev in revs:
             target = getinfo(rev)
             match = True
             for n, f in enumerate(getfieldfuncs):
                 if target[n] != f(x):
                     match = False
             if match:
                 return True
         return False
 
     return subset.filter(matches, condrepr=('<matching%r %r>', fields, revs))
 
 @predicate('reverse(set)', safe=True)
 def reverse(repo, subset, x):
     """Reverse order of set.
     """
     l = getset(repo, subset, x)
     l.reverse()
     return l
 
 @predicate('roots(set)', safe=True)
 def roots(repo, subset, x):
     """Changesets in set with no parent changeset in set.
     """
     s = getset(repo, fullreposet(repo), x)
     parents = repo.changelog.parentrevs
     def filter(r):
         for p in parents(r):
             if 0 <= p and p in s:
                 return False
         return True
     return subset & s.filter(filter, condrepr='<roots>')
 
 @predicate('sort(set[, [-]key...])', safe=True)
 def sort(repo, subset, x):
     """Sort set by keys. The default sort order is ascending, specify a key
     as ``-key`` to sort in descending order.
 
     The keys can be:
 
     - ``rev`` for the revision number,
     - ``branch`` for the branch name,
     - ``desc`` for the commit message (description),
     - ``user`` for user name (``author`` can be used as an alias),
     - ``date`` for the commit date
     """
     # i18n: "sort" is a keyword
     l = getargs(x, 1, 2, _("sort requires one or two arguments"))
     keys = "rev"
     if len(l) == 2:
         # i18n: "sort" is a keyword
         keys = getstring(l[1], _("sort spec must be a string"))
 
     s = l[0]
     keys = keys.split()
     l = []
     def invert(s):
         return "".join(chr(255 - ord(c)) for c in s)
     revs = getset(repo, subset, s)
     if keys == ["rev"]:
         revs.sort()
         return revs
     elif keys == ["-rev"]:
         revs.sort(reverse=True)
         return revs
     for r in revs:
         c = repo[r]
         e = []
         for k in keys:
             if k == 'rev':
                 e.append(r)
             elif k == '-rev':
                 e.append(-r)
             elif k == 'branch':
                 e.append(c.branch())
             elif k == '-branch':
                 e.append(invert(c.branch()))
             elif k == 'desc':
                 e.append(c.description())
             elif k == '-desc':
                 e.append(invert(c.description()))
             elif k in 'user author':
                 e.append(c.user())
             elif k in '-user -author':
                 e.append(invert(c.user()))
             elif k == 'date':
                 e.append(c.date()[0])
             elif k == '-date':
                 e.append(-c.date()[0])
             else:
                 raise error.ParseError(_("unknown sort key %r") % k)
         e.append(r)
         l.append(e)
     l.sort()
     return baseset([e[-1] for e in l])
 
 @predicate('subrepo([pattern])')
 def subrepo(repo, subset, x):
     """Changesets that add, modify or remove the given subrepo.  If no subrepo
     pattern is named, any subrepo changes are returned.
     """
     # i18n: "subrepo" is a keyword
     args = getargs(x, 0, 1, _('subrepo takes at most one argument'))
     pat = None
     if len(args) != 0:
         pat = getstring(args[0], _("subrepo requires a pattern"))
 
     m = matchmod.exact(repo.root, repo.root, ['.hgsubstate'])
 
     def submatches(names):
         k, p, m = util.stringmatcher(pat)
         for name in names:
             if m(name):
                 yield name
 
     def matches(x):
         c = repo[x]
         s = repo.status(c.p1().node(), c.node(), match=m)
 
         if pat is None:
             return s.added or s.modified or s.removed
 
         if s.added:
             return any(submatches(c.substate.keys()))
 
         if s.modified:
             subs = set(c.p1().substate.keys())
             subs.update(c.substate.keys())
 
             for path in submatches(subs):
                 if c.p1().substate.get(path) != c.substate.get(path):
                     return True
 
         if s.removed:
             return any(submatches(c.p1().substate.keys()))
 
         return False
 
     return subset.filter(matches, condrepr=('<subrepo %r>', pat))
 
 def _substringmatcher(pattern):
     kind, pattern, matcher = util.stringmatcher(pattern)
     if kind == 'literal':
         matcher = lambda s: pattern in s
     return kind, pattern, matcher
 
 @predicate('tag([name])', safe=True)
 def tag(repo, subset, x):
     """The specified tag by name, or all tagged revisions if no name is given.
 
     If `name` starts with `re:`, the remainder of the name is treated as
     a regular expression. To match a tag that actually starts with `re:`,
     use the prefix `literal:`.
     """
     # i18n: "tag" is a keyword
     args = getargs(x, 0, 1, _("tag takes one or no arguments"))
     cl = repo.changelog
     if args:
         pattern = getstring(args[0],
                             # i18n: "tag" is a keyword
                             _('the argument to tag must be a string'))
         kind, pattern, matcher = util.stringmatcher(pattern)
         if kind == 'literal':
             # avoid resolving all tags
             tn = repo._tagscache.tags.get(pattern, None)
             if tn is None:
                 raise error.RepoLookupError(_("tag '%s' does not exist")
                                             % pattern)
             s = set([repo[tn].rev()])
         else:
             s = set([cl.rev(n) for t, n in repo.tagslist() if matcher(t)])
     else:
         s = set([cl.rev(n) for t, n in repo.tagslist() if t != 'tip'])
     return subset & s
 
 @predicate('tagged', safe=True)
 def tagged(repo, subset, x):
     return tag(repo, subset, x)
 
 @predicate('unstable()', safe=True)
 def unstable(repo, subset, x):
     """Non-obsolete changesets with obsolete ancestors.
     """
     # i18n: "unstable" is a keyword
     getargs(x, 0, 0, _("unstable takes no arguments"))
     unstables = obsmod.getrevs(repo, 'unstable')
     return subset & unstables
 
 
 @predicate('user(string)', safe=True)
 def user(repo, subset, x):
     """User name contains string. The match is case-insensitive.
 
     If `string` starts with `re:`, the remainder of the string is treated as
     a regular expression. To match a user that actually contains `re:`, use
     the prefix `literal:`.
     """
     return author(repo, subset, x)
 
 # experimental
 @predicate('wdir', safe=True)
 def wdir(repo, subset, x):
     # i18n: "wdir" is a keyword
     getargs(x, 0, 0, _("wdir takes no arguments"))
     if node.wdirrev in subset or isinstance(subset, fullreposet):
         return baseset([node.wdirrev])
     return baseset()
 
 # for internal use
 @predicate('_list', safe=True)
 def _list(repo, subset, x):
     s = getstring(x, "internal error")
     if not s:
         return baseset()
     # remove duplicates here. it's difficult for caller to deduplicate sets
     # because different symbols can point to the same rev.
     cl = repo.changelog
     ls = []
     seen = set()
     for t in s.split('\0'):
         try:
             # fast path for integer revision
             r = int(t)
             if str(r) != t or r not in cl:
                 raise ValueError
             revs = [r]
         except ValueError:
             revs = stringset(repo, subset, t)
 
         for r in revs:
             if r in seen:
                 continue
             if (r in subset
                 or r == node.nullrev and isinstance(subset, fullreposet)):
                 ls.append(r)
             seen.add(r)
     return baseset(ls)
 
 # for internal use
 @predicate('_intlist', safe=True)
 def _intlist(repo, subset, x):
     s = getstring(x, "internal error")
     if not s:
         return baseset()
     ls = [int(r) for r in s.split('\0')]
     s = subset
     return baseset([r for r in ls if r in s])
 
 # for internal use
 @predicate('_hexlist', safe=True)
 def _hexlist(repo, subset, x):
     s = getstring(x, "internal error")
     if not s:
         return baseset()
     cl = repo.changelog
     ls = [cl.rev(node.bin(r)) for r in s.split('\0')]
     s = subset
     return baseset([r for r in ls if r in s])
 
 methods = {
     "range": rangeset,
     "dagrange": dagrange,
     "string": stringset,
     "symbol": stringset,
     "and": andset,
     "or": orset,
     "not": notset,
     "difference": differenceset,
     "list": listset,
     "keyvalue": keyvaluepair,
     "func": func,
     "ancestor": ancestorspec,
     "parent": parentspec,
     "parentpost": p1,
 }
 
 def optimize(x, small):
     if x is None:
         return 0, x
 
     smallbonus = 1
     if small:
         smallbonus = .5
 
     op = x[0]
     if op == 'minus':
         return optimize(('and', x[1], ('not', x[2])), small)
     elif op == 'only':
         return optimize(('func', ('symbol', 'only'),
                          ('list', x[1], x[2])), small)
     elif op == 'onlypost':
         return optimize(('func', ('symbol', 'only'), x[1]), small)
     elif op == 'dagrangepre':
         return optimize(('func', ('symbol', 'ancestors'), x[1]), small)
     elif op == 'dagrangepost':
         return optimize(('func', ('symbol', 'descendants'), x[1]), small)
     elif op == 'rangeall':
         return optimize(('range', ('string', '0'), ('string', 'tip')), small)
     elif op == 'rangepre':
         return optimize(('range', ('string', '0'), x[1]), small)
     elif op == 'rangepost':
         return optimize(('range', x[1], ('string', 'tip')), small)
     elif op == 'negate':
         return optimize(('string',
                          '-' + getstring(x[1], _("can't negate that"))), small)
     elif op in 'string symbol negate':
         return smallbonus, x # single revisions are small
     elif op == 'and':
         wa, ta = optimize(x[1], True)
         wb, tb = optimize(x[2], True)
 
         # (::x and not ::y)/(not ::y and ::x) have a fast path
         def isonly(revs, bases):
             return (
                 revs is not None
                 and revs[0] == 'func'
                 and getstring(revs[1], _('not a symbol')) == 'ancestors'
                 and bases is not None
                 and bases[0] == 'not'
                 and bases[1][0] == 'func'
                 and getstring(bases[1][1], _('not a symbol')) == 'ancestors')
 
         w = min(wa, wb)
         if isonly(ta, tb):
             return w, ('func', ('symbol', 'only'), ('list', ta[2], tb[1][2]))
         if isonly(tb, ta):
             return w, ('func', ('symbol', 'only'), ('list', tb[2], ta[1][2]))
 
         if tb is not None and tb[0] == 'not':
             return wa, ('difference', ta, tb[1])
 
         if wa > wb:
             return w, (op, tb, ta)
         return w, (op, ta, tb)
     elif op == 'or':
         # fast path for machine-generated expression, that is likely to have
         # lots of trivial revisions: 'a + b + c()' to '_list(a b) + c()'
         ws, ts, ss = [], [], []
         def flushss():
             if not ss:
                 return
             if len(ss) == 1:
                 w, t = ss[0]
             else:
                 s = '\0'.join(t[1] for w, t in ss)
                 y = ('func', ('symbol', '_list'), ('string', s))
                 w, t = optimize(y, False)
             ws.append(w)
             ts.append(t)
             del ss[:]
         for y in x[1:]:
             w, t = optimize(y, False)
             if t is not None and (t[0] == 'string' or t[0] == 'symbol'):
                 ss.append((w, t))
                 continue
             flushss()
             ws.append(w)
             ts.append(t)
         flushss()
         if len(ts) == 1:
             return ws[0], ts[0] # 'or' operation is fully optimized out
         # we can't reorder trees by weight because it would change the order.
         # ("sort(a + b)" == "sort(b + a)", but "a + b" != "b + a")
         #   ts = tuple(t for w, t in sorted(zip(ws, ts), key=lambda wt: wt[0]))
         return max(ws), (op,) + tuple(ts)
     elif op == 'not':
         # Optimize not public() to _notpublic() because we have a fast version
         if x[1] == ('func', ('symbol', 'public'), None):
             newsym = ('func', ('symbol', '_notpublic'), None)
             o = optimize(newsym, not small)
             return o[0], o[1]
         else:
             o = optimize(x[1], not small)
             return o[0], (op, o[1])
     elif op == 'parentpost':
         o = optimize(x[1], small)
         return o[0], (op, o[1])
     elif op == 'group':
         return optimize(x[1], small)
     elif op in 'dagrange range parent ancestorspec':
         if op == 'parent':
             # x^:y means (x^) : y, not x ^ (:y)
             post = ('parentpost', x[1])
             if x[2][0] == 'dagrangepre':
                 return optimize(('dagrange', post, x[2][1]), small)
             elif x[2][0] == 'rangepre':
                 return optimize(('range', post, x[2][1]), small)
 
         wa, ta = optimize(x[1], small)
         wb, tb = optimize(x[2], small)
         return wa + wb, (op, ta, tb)
     elif op == 'list':
         ws, ts = zip(*(optimize(y, small) for y in x[1:]))
         return sum(ws), (op,) + ts
     elif op == 'func':
         f = getstring(x[1], _("not a symbol"))
         wa, ta = optimize(x[2], small)
         if f in ("author branch closed date desc file grep keyword "
                  "outgoing user"):
             w = 10 # slow
         elif f in "modifies adds removes":
             w = 30 # slower
         elif f == "contains":
             w = 100 # very slow
         elif f == "ancestor":
             w = 1 * smallbonus
         elif f in "reverse limit first _intlist":
             w = 0
         elif f in "sort":
             w = 10 # assume most sorts look at changelog
         else:
             w = 1
         return w + wa, (op, x[1], ta)
     return 1, x
 
 # the set of valid characters for the initial letter of symbols in
 # alias declarations and definitions
 _aliassyminitletters = set(c for c in [chr(i) for i in xrange(256)]
                            if c.isalnum() or c in '._@$' or ord(c) > 127)
 
 def _tokenizealias(program, lookup=None):
     """Parse alias declaration/definition into a stream of tokens
 
     This allows symbol names to use also ``$`` as an initial letter
     (for backward compatibility), and callers of this function should
     examine whether ``$`` is used also for unexpected symbols or not.
     """
     return tokenize(program, lookup=lookup,
                     syminitletters=_aliassyminitletters)
 
 def _parsealiasdecl(decl):
     """Parse alias declaration ``decl``
 
     This returns ``(name, tree, args, errorstr)`` tuple:
 
     - ``name``: of declared alias (may be ``decl`` itself at error)
     - ``tree``: parse result (or ``None`` at error)
     - ``args``: list of alias argument names (or None for symbol declaration)
     - ``errorstr``: detail about detected error (or None)
 
     >>> _parsealiasdecl('foo')
     ('foo', ('symbol', 'foo'), None, None)
     >>> _parsealiasdecl('$foo')
     ('$foo', None, None, "'$' not for alias arguments")
     >>> _parsealiasdecl('foo::bar')
     ('foo::bar', None, None, 'invalid format')
     >>> _parsealiasdecl('foo bar')
     ('foo bar', None, None, 'at 4: invalid token')
     >>> _parsealiasdecl('foo()')
     ('foo', ('func', ('symbol', 'foo')), [], None)
     >>> _parsealiasdecl('$foo()')
     ('$foo()', None, None, "'$' not for alias arguments")
     >>> _parsealiasdecl('foo($1, $2)')
     ('foo', ('func', ('symbol', 'foo')), ['$1', '$2'], None)
     >>> _parsealiasdecl('foo(bar_bar, baz.baz)')
     ('foo', ('func', ('symbol', 'foo')), ['bar_bar', 'baz.baz'], None)
     >>> _parsealiasdecl('foo($1, $2, nested($1, $2))')
     ('foo($1, $2, nested($1, $2))', None, None, 'invalid argument list')
     >>> _parsealiasdecl('foo(bar($1, $2))')
     ('foo(bar($1, $2))', None, None, 'invalid argument list')
     >>> _parsealiasdecl('foo("string")')
     ('foo("string")', None, None, 'invalid argument list')
     >>> _parsealiasdecl('foo($1, $2')
     ('foo($1, $2', None, None, 'at 10: unexpected token: end')
     >>> _parsealiasdecl('foo("string')
     ('foo("string', None, None, 'at 5: unterminated string')
     >>> _parsealiasdecl('foo($1, $2, $1)')
     ('foo', None, None, 'argument names collide with each other')
     """
     p = parser.parser(elements)
     try:
         tree, pos = p.parse(_tokenizealias(decl))
         if (pos != len(decl)):
             raise error.ParseError(_('invalid token'), pos)
         tree = parser.simplifyinfixops(tree, ('list',))
     except error.ParseError as inst:
         return (decl, None, None, parser.parseerrordetail(inst))
 
     if True:  # XXX to be removed
         if tree[0] == 'symbol':
             # "name = ...." style
             name = tree[1]
             if name.startswith('$'):
                 return (decl, None, None, _("'$' not for alias arguments"))
             return (name, tree, None, None)
 
         if tree[0] == 'func' and tree[1][0] == 'symbol':
             # "name(arg, ....) = ...." style
             name = tree[1][1]
             if name.startswith('$'):
                 return (decl, None, None, _("'$' not for alias arguments"))
             args = []
             for arg in getlist(tree[2]):
                 if arg[0] != 'symbol':
                     return (decl, None, None, _("invalid argument list"))
                 args.append(arg[1])
             if len(args) != len(set(args)):
                 return (name, None, None,
                         _("argument names collide with each other"))
             return (name, tree[:2], args, None)
 
         return (decl, None, None, _("invalid format"))
 
 def _relabelaliasargs(tree, args):
     if not isinstance(tree, tuple):
         return tree
     op = tree[0]
     if op != 'symbol':
         return (op,) + tuple(_relabelaliasargs(x, args) for x in tree[1:])
 
     assert len(tree) == 2
     sym = tree[1]
     if sym in args:
         op = '_aliasarg'
     elif sym.startswith('$'):
         raise error.ParseError(_("'$' not for alias arguments"))
     return (op, sym)
 
 def _parsealiasdefn(defn, args):
     """Parse alias definition ``defn``
 
     This function marks alias argument references as ``_aliasarg``.
 
     ``args`` is a list of alias argument names, or None if the alias
     is declared as a symbol.
 
     This returns "tree" as parsing result.
 
     >>> def prettyformat(tree):
     ...     return parser.prettyformat(tree, ('_aliasarg', 'string', 'symbol'))
     >>> args = ['$1', '$2', 'foo']
     >>> print prettyformat(_parsealiasdefn('$1 or foo', args))
     (or
       ('_aliasarg', '$1')
       ('_aliasarg', 'foo'))
     >>> try:
     ...     _parsealiasdefn('$1 or $bar', args)
     ... except error.ParseError, inst:
     ...     print parser.parseerrordetail(inst)
     '$' not for alias arguments
     >>> args = ['$1', '$10', 'foo']
     >>> print prettyformat(_parsealiasdefn('$10 or foobar', args))
     (or
       ('_aliasarg', '$10')
       ('symbol', 'foobar'))
     >>> print prettyformat(_parsealiasdefn('"$1" or "foo"', args))
     (or
       ('string', '$1')
       ('string', 'foo'))
     """
     if args:
         args = set(args)
     else:
         args = set()
 
     p = parser.parser(elements)
     tree, pos = p.parse(_tokenizealias(defn))
     if pos != len(defn):
         raise error.ParseError(_('invalid token'), pos)
     tree = parser.simplifyinfixops(tree, ('list', 'or'))
     return _relabelaliasargs(tree, args)
 
+class _aliasrules(parser.basealiasrules):
+    """Parsing and expansion rule set of revset aliases"""
+    _section = _('revset alias')
+    _getlist = staticmethod(getlist)
+
 class revsetalias(object):
     # whether own `error` information is already shown or not.
     # this avoids showing same warning multiple times at each `findaliases`.
     warned = False
 
     def __init__(self, name, value):
         '''Aliases like:
 
         h = heads(default)
         b($1) = ancestors($1) - ancestors(default)
         '''
         self.name, self.tree, self.args, self.error = _parsealiasdecl(name)
         if self.error:
             self.error = _('failed to parse the declaration of revset alias'
                            ' "%s": %s') % (self.name, self.error)
             return
 
         try:
             self.replacement = _parsealiasdefn(value, self.args)
         except error.ParseError as inst:
             self.error = _('failed to parse the definition of revset alias'
                            ' "%s": %s') % (self.name,
                                            parser.parseerrordetail(inst))
 
 def _getalias(aliases, tree):
     """If tree looks like an unexpanded alias, return it. Return None
     otherwise.
     """
     if isinstance(tree, tuple):
         if tree[0] == 'symbol':
             name = tree[1]
             alias = aliases.get(name)
             if alias and alias.args is None and alias.tree == tree:
                 return alias
         if tree[0] == 'func':
             if tree[1][0] == 'symbol':
                 name = tree[1][1]
                 alias = aliases.get(name)
                 if alias and alias.args is not None and alias.tree == tree[:2]:
                     return alias
     return None
 
 def _expandargs(tree, args):
     """Replace _aliasarg instances with the substitution value of the
     same name in args, recursively.
     """
     if not isinstance(tree, tuple):
         return tree
     if tree[0] == '_aliasarg':
         sym = tree[1]
         return args[sym]
     return tuple(_expandargs(t, args) for t in tree)
 
 def _expandaliases(aliases, tree, expanding, cache):
     """Expand aliases in tree, recursively.
 
     'aliases' is a dictionary mapping user defined aliases to
     revsetalias objects.
     """
     if not isinstance(tree, tuple):
         # Do not expand raw strings
         return tree
     alias = _getalias(aliases, tree)
     if alias is not None:
         if alias.error:
             raise error.Abort(alias.error)
         if alias in expanding:
             raise error.ParseError(_('infinite expansion of revset alias "%s" '
                                      'detected') % alias.name)
         expanding.append(alias)
         if alias.name not in cache:
             cache[alias.name] = _expandaliases(aliases, alias.replacement,
                                                expanding, cache)
         result = cache[alias.name]
         expanding.pop()
         if alias.args is not None:
             l = getlist(tree[2])
             if len(l) != len(alias.args):
                 raise error.ParseError(
                     _('invalid number of arguments: %d') % len(l))
             l = [_expandaliases(aliases, a, [], cache) for a in l]
             result = _expandargs(result, dict(zip(alias.args, l)))
     else:
         result = tuple(_expandaliases(aliases, t, expanding, cache)
                        for t in tree)
     return result
 
 def findaliases(ui, tree, showwarning=None):
     aliases = {}
     for k, v in ui.configitems('revsetalias'):
         alias = revsetalias(k, v)
         aliases[alias.name] = alias
     tree = _expandaliases(aliases, tree, [], {})
     if showwarning:
         # warn about problematic (but not referred) aliases
         for name, alias in sorted(aliases.iteritems()):
             if alias.error and not alias.warned:
                 showwarning(_('warning: %s\n') % (alias.error))
                 alias.warned = True
     return tree
 
 def foldconcat(tree):
     """Fold elements to be concatenated by `##`
     """
     if not isinstance(tree, tuple) or tree[0] in ('string', 'symbol'):
         return tree
     if tree[0] == '_concat':
         pending = [tree]
         l = []
         while pending:
             e = pending.pop()
             if e[0] == '_concat':
                 pending.extend(reversed(e[1:]))
             elif e[0] in ('string', 'symbol'):
                 l.append(e[1])
             else:
                 msg = _("\"##\" can't concatenate \"%s\" element") % (e[0])
                 raise error.ParseError(msg)
         return ('string', ''.join(l))
     else:
         return tuple(foldconcat(t) for t in tree)
 
 def parse(spec, lookup=None):
     p = parser.parser(elements)
     tree, pos = p.parse(tokenize(spec, lookup=lookup))
     if pos != len(spec):
         raise error.ParseError(_("invalid token"), pos)
     return parser.simplifyinfixops(tree, ('list', 'or'))
 
 def posttreebuilthook(tree, repo):
     # hook for extensions to execute code on the optimized tree
     pass
 
 def match(ui, spec, repo=None):
     if not spec:
         raise error.ParseError(_("empty query"))
     lookup = None
     if repo:
         lookup = repo.__contains__
     tree = parse(spec, lookup)
     return _makematcher(ui, tree, repo)
 
 def matchany(ui, specs, repo=None):
     """Create a matcher that will include any revisions matching one of the
     given specs"""
     if not specs:
         def mfunc(repo, subset=None):
             return baseset()
         return mfunc
     if not all(specs):
         raise error.ParseError(_("empty query"))
     lookup = None
     if repo:
         lookup = repo.__contains__
     if len(specs) == 1:
         tree = parse(specs[0], lookup)
     else:
         tree = ('or',) + tuple(parse(s, lookup) for s in specs)
     return _makematcher(ui, tree, repo)
 
 def _makematcher(ui, tree, repo):
     if ui:
         tree = findaliases(ui, tree, showwarning=ui.warn)
     tree = foldconcat(tree)
     weight, tree = optimize(tree, True)
     posttreebuilthook(tree, repo)
     def mfunc(repo, subset=None):
         if subset is None:
             subset = fullreposet(repo)
         if util.safehasattr(subset, 'isascending'):
             result = getset(repo, subset, tree)
         else:
             result = getset(repo, baseset(subset), tree)
         return result
     return mfunc
 
 def formatspec(expr, *args):
     '''
     This is a convenience function for using revsets internally, and
     escapes arguments appropriately. Aliases are intentionally ignored
     so that intended expression behavior isn't accidentally subverted.
 
     Supported arguments:
 
     %r = revset expression, parenthesized
     %d = int(arg), no quoting
     %s = string(arg), escaped and single-quoted
     %b = arg.branch(), escaped and single-quoted
     %n = hex(arg), single-quoted
     %% = a literal '%'
 
     Prefixing the type with 'l' specifies a parenthesized list of that type.
 
     >>> formatspec('%r:: and %lr', '10 or 11', ("this()", "that()"))
     '(10 or 11):: and ((this()) or (that()))'
     >>> formatspec('%d:: and not %d::', 10, 20)
     '10:: and not 20::'
     >>> formatspec('%ld or %ld', [], [1])
     "_list('') or 1"
     >>> formatspec('keyword(%s)', 'foo\\xe9')
     "keyword('foo\\\\xe9')"
     >>> b = lambda: 'default'
     >>> b.branch = b
     >>> formatspec('branch(%b)', b)
     "branch('default')"
     >>> formatspec('root(%ls)', ['a', 'b', 'c', 'd'])
     "root(_list('a\\x00b\\x00c\\x00d'))"
     '''
 
     def quote(s):
         return repr(str(s))
 
     def argtype(c, arg):
         if c == 'd':
             return str(int(arg))
         elif c == 's':
             return quote(arg)
         elif c == 'r':
             parse(arg) # make sure syntax errors are confined
             return '(%s)' % arg
         elif c == 'n':
             return quote(node.hex(arg))
         elif c == 'b':
             return quote(arg.branch())
 
     def listexp(s, t):
         l = len(s)
         if l == 0:
             return "_list('')"
         elif l == 1:
             return argtype(t, s[0])
         elif t == 'd':
             return "_intlist('%s')" % "\0".join(str(int(a)) for a in s)
         elif t == 's':
             return "_list('%s')" % "\0".join(s)
         elif t == 'n':
             return "_hexlist('%s')" % "\0".join(node.hex(a) for a in s)
         elif t == 'b':
             return "_list('%s')" % "\0".join(a.branch() for a in s)
 
         m = l // 2
         return '(%s or %s)' % (listexp(s[:m], t), listexp(s[m:], t))
 
     ret = ''
     pos = 0
     arg = 0
     while pos < len(expr):
         c = expr[pos]
         if c == '%':
             pos += 1
             d = expr[pos]
             if d == '%':
                 ret += d
             elif d in 'dsnbr':
                 ret += argtype(d, args[arg])
                 arg += 1
             elif d == 'l':
                 # a list of some type
                 pos += 1
                 d = expr[pos]
                 ret += listexp(list(args[arg]), d)
                 arg += 1
             else:
                 raise error.Abort('unexpected revspec format character %s' % d)
         else:
             ret += c
         pos += 1
 
     return ret
 
 def prettyformat(tree):
     return parser.prettyformat(tree, ('string', 'symbol'))
 
 def depth(tree):
     if isinstance(tree, tuple):
         return max(map(depth, tree)) + 1
     else:
         return 0
 
 def funcsused(tree):
     if not isinstance(tree, tuple) or tree[0] in ('string', 'symbol'):
         return set()
     else:
         funcs = set()
         for s in tree[1:]:
             funcs |= funcsused(s)
         if tree[0] == 'func':
             funcs.add(tree[1][1])
         return funcs
 
 def _formatsetrepr(r):
     """Format an optional printable representation of a set
 
     ========  =================================
     type(r)   example
     ========  =================================
     tuple     ('<not %r>', other)
     str       '<branch closed>'
     callable  lambda: '<branch %r>' % sorted(b)
     object    other
     ========  =================================
     """
     if r is None:
         return ''
     elif isinstance(r, tuple):
         return r[0] % r[1:]
     elif isinstance(r, str):
         return r
     elif callable(r):
         return r()
     else:
         return repr(r)
 
 class abstractsmartset(object):
 
     def __nonzero__(self):
         """True if the smartset is not empty"""
         raise NotImplementedError()
 
     def __contains__(self, rev):
         """provide fast membership testing"""
         raise NotImplementedError()
 
     def __iter__(self):
         """iterate the set in the order it is supposed to be iterated"""
         raise NotImplementedError()
 
     # Attributes containing a function to perform a fast iteration in a given
     # direction. A smartset can have none, one, or both defined.
     #
     # Default value is None instead of a function returning None to avoid
     # initializing an iterator just for testing if a fast method exists.
     fastasc = None
     fastdesc = None
 
     def isascending(self):
         """True if the set will iterate in ascending order"""
         raise NotImplementedError()
 
     def isdescending(self):
         """True if the set will iterate in descending order"""
         raise NotImplementedError()
 
     @util.cachefunc
     def min(self):
         """return the minimum element in the set"""
         if self.fastasc is not None:
             for r in self.fastasc():
                 return r
             raise ValueError('arg is an empty sequence')
         return min(self)
 
     @util.cachefunc
     def max(self):
         """return the maximum element in the set"""
         if self.fastdesc is not None:
             for r in self.fastdesc():
                 return r
             raise ValueError('arg is an empty sequence')
         return max(self)
 
     def first(self):
         """return the first element in the set (user iteration perspective)
 
         Return None if the set is empty"""
         raise NotImplementedError()
 
     def last(self):
         """return the last element in the set (user iteration perspective)
 
         Return None if the set is empty"""
         raise NotImplementedError()
 
     def __len__(self):
         """return the length of the smartsets
 
         This can be expensive on smartset that could be lazy otherwise."""
         raise NotImplementedError()
 
     def reverse(self):
         """reverse the expected iteration order"""
         raise NotImplementedError()
 
     def sort(self, reverse=True):
         """get the set to iterate in an ascending or descending order"""
         raise NotImplementedError()
 
     def __and__(self, other):
         """Returns a new object with the intersection of the two collections.
 
         This is part of the mandatory API for smartset."""
         if isinstance(other, fullreposet):
             return self
         return self.filter(other.__contains__, condrepr=other, cache=False)
 
     def __add__(self, other):
         """Returns a new object with the union of the two collections.
 
         This is part of the mandatory API for smartset."""
         return addset(self, other)
 
     def __sub__(self, other):
         """Returns a new object with the substraction of the two collections.
 
         This is part of the mandatory API for smartset."""
         c = other.__contains__
         return self.filter(lambda r: not c(r), condrepr=('<not %r>', other),
                            cache=False)
 
     def filter(self, condition, condrepr=None, cache=True):
         """Returns this smartset filtered by condition as a new smartset.
 
         `condition` is a callable which takes a revision number and returns a
         boolean. Optional `condrepr` provides a printable representation of
         the given `condition`.
 
         This is part of the mandatory API for smartset."""
         # builtin cannot be cached. but do not needs to
         if cache and util.safehasattr(condition, 'func_code'):
             condition = util.cachefunc(condition)
         return filteredset(self, condition, condrepr)
 
 class baseset(abstractsmartset):
     """Basic data structure that represents a revset and contains the basic
     operation that it should be able to perform.
 
     Every method in this class should be implemented by any smartset class.
     """
     def __init__(self, data=(), datarepr=None):
         """
         datarepr: a tuple of (format, obj, ...), a function or an object that
                   provides a printable representation of the given data.
         """
         self._ascending = None
         if not isinstance(data, list):
             if isinstance(data, set):
                 self._set = data
                 # set has no order we pick one for stability purpose
                 self._ascending = True
             data = list(data)
         self._list = data
         self._datarepr = datarepr
 
     @util.propertycache
     def _set(self):
         return set(self._list)
 
     @util.propertycache
     def _asclist(self):
         asclist = self._list[:]
         asclist.sort()
         return asclist
 
     def __iter__(self):
         if self._ascending is None:
             return iter(self._list)
         elif self._ascending:
             return iter(self._asclist)
         else:
             return reversed(self._asclist)
 
     def fastasc(self):
         return iter(self._asclist)
 
     def fastdesc(self):
         return reversed(self._asclist)
 
     @util.propertycache
     def __contains__(self):
         return self._set.__contains__
 
     def __nonzero__(self):
         return bool(self._list)
 
     def sort(self, reverse=False):
         self._ascending = not bool(reverse)
 
     def reverse(self):
         if self._ascending is None:
             self._list.reverse()
         else:
             self._ascending = not self._ascending
 
     def __len__(self):
         return len(self._list)
 
     def isascending(self):
         """Returns True if the collection is ascending order, False if not.
 
         This is part of the mandatory API for smartset."""
         if len(self) <= 1:
             return True
         return self._ascending is not None and self._ascending
 
     def isdescending(self):
         """Returns True if the collection is descending order, False if not.
 
         This is part of the mandatory API for smartset."""
         if len(self) <= 1:
             return True
         return self._ascending is not None and not self._ascending
 
     def first(self):
         if self:
             if self._ascending is None:
                 return self._list[0]
             elif self._ascending:
                 return self._asclist[0]
             else:
                 return self._asclist[-1]
         return None
 
     def last(self):
         if self:
             if self._ascending is None:
                 return self._list[-1]
             elif self._ascending:
                 return self._asclist[-1]
             else:
                 return self._asclist[0]
         return None
 
     def __repr__(self):
         d = {None: '', False: '-', True: '+'}[self._ascending]
         s = _formatsetrepr(self._datarepr)
         if not s:
             l = self._list
             # if _list has been built from a set, it might have a different
             # order from one python implementation to another.
             # We fallback to the sorted version for a stable output.
             if self._ascending is not None:
                 l = self._asclist
             s = repr(l)
         return '<%s%s %s>' % (type(self).__name__, d, s)
 
 class filteredset(abstractsmartset):
     """Duck type for baseset class which iterates lazily over the revisions in
     the subset and contains a function which tests for membership in the
     revset
     """
     def __init__(self, subset, condition=lambda x: True, condrepr=None):
         """
         condition: a function that decide whether a revision in the subset
                    belongs to the revset or not.
         condrepr: a tuple of (format, obj, ...), a function or an object that
                   provides a printable representation of the given condition.
         """
         self._subset = subset
         self._condition = condition
         self._condrepr = condrepr
 
     def __contains__(self, x):
         return x in self._subset and self._condition(x)
 
     def __iter__(self):
         return self._iterfilter(self._subset)
 
     def _iterfilter(self, it):
         cond = self._condition
         for x in it:
             if cond(x):
                 yield x
 
     @property
     def fastasc(self):
         it = self._subset.fastasc
         if it is None:
             return None
         return lambda: self._iterfilter(it())
 
     @property
     def fastdesc(self):
         it = self._subset.fastdesc
         if it is None:
             return None
         return lambda: self._iterfilter(it())
 
     def __nonzero__(self):
         fast = self.fastasc
         if fast is None:
             fast = self.fastdesc
         if fast is not None:
             it = fast()
         else:
             it = self
 
         for r in it:
             return True
         return False
 
     def __len__(self):
         # Basic implementation to be changed in future patches.
         # until this gets improved, we use generator expression
         # here, since list compr is free to call __len__ again
         # causing infinite recursion
         l = baseset(r for r in self)
         return len(l)
 
     def sort(self, reverse=False):
         self._subset.sort(reverse=reverse)
 
     def reverse(self):
         self._subset.reverse()
 
     def isascending(self):
         return self._subset.isascending()
 
     def isdescending(self):
         return self._subset.isdescending()
 
     def first(self):
         for x in self:
             return x
         return None
 
     def last(self):
         it = None
         if self.isascending():
             it = self.fastdesc
         elif self.isdescending():
             it = self.fastasc
         if it is not None:
             for x in it():
                 return x
             return None #empty case
         else:
             x = None
             for x in self:
                 pass
             return x
 
     def __repr__(self):
         xs = [repr(self._subset)]
         s = _formatsetrepr(self._condrepr)
         if s:
             xs.append(s)
         return '<%s %s>' % (type(self).__name__, ', '.join(xs))
 
 def _iterordered(ascending, iter1, iter2):
     """produce an ordered iteration from two iterators with the same order
 
     The ascending is used to indicated the iteration direction.
     """
     choice = max
     if ascending:
         choice = min
 
     val1 = None
     val2 = None
     try:
         # Consume both iterators in an ordered way until one is empty
         while True:
             if val1 is None:
                 val1 = iter1.next()
             if val2 is None:
                 val2 = iter2.next()
             next = choice(val1, val2)
             yield next
             if val1 == next:
                 val1 = None
             if val2 == next:
                 val2 = None
     except StopIteration:
         # Flush any remaining values and consume the other one
         it = iter2
         if val1 is not None:
             yield val1
             it = iter1
         elif val2 is not None:
             # might have been equality and both are empty
             yield val2
         for val in it:
             yield val
 
 class addset(abstractsmartset):
     """Represent the addition of two sets
 
     Wrapper structure for lazily adding two structures without losing much
     performance on the __contains__ method
 
     If the ascending attribute is set, that means the two structures are
     ordered in either an ascending or descending way. Therefore, we can add
     them maintaining the order by iterating over both at the same time
 
     >>> xs = baseset([0, 3, 2])
     >>> ys = baseset([5, 2, 4])
 
     >>> rs = addset(xs, ys)
     >>> bool(rs), 0 in rs, 1 in rs, 5 in rs, rs.first(), rs.last()
     (True, True, False, True, 0, 4)
     >>> rs = addset(xs, baseset([]))
     >>> bool(rs), 0 in rs, 1 in rs, rs.first(), rs.last()
     (True, True, False, 0, 2)
     >>> rs = addset(baseset([]), baseset([]))
     >>> bool(rs), 0 in rs, rs.first(), rs.last()
     (False, False, None, None)
 
     iterate unsorted:
     >>> rs = addset(xs, ys)
     >>> # (use generator because pypy could call len())
     >>> list(x for x in rs)  # without _genlist
     [0, 3, 2, 5, 4]
     >>> assert not rs._genlist
     >>> len(rs)
     5
     >>> [x for x in rs]  # with _genlist
     [0, 3, 2, 5, 4]
     >>> assert rs._genlist
 
     iterate ascending:
     >>> rs = addset(xs, ys, ascending=True)
     >>> # (use generator because pypy could call len())
     >>> list(x for x in rs), list(x for x in rs.fastasc())  # without _asclist
     ([0, 2, 3, 4, 5], [0, 2, 3, 4, 5])
     >>> assert not rs._asclist
     >>> len(rs)
     5
     >>> [x for x in rs], [x for x in rs.fastasc()]
     ([0, 2, 3, 4, 5], [0, 2, 3, 4, 5])
     >>> assert rs._asclist
 
     iterate descending:
     >>> rs = addset(xs, ys, ascending=False)
     >>> # (use generator because pypy could call len())
     >>> list(x for x in rs), list(x for x in rs.fastdesc())  # without _asclist
     ([5, 4, 3, 2, 0], [5, 4, 3, 2, 0])
     >>> assert not rs._asclist
     >>> len(rs)
     5
     >>> [x for x in rs], [x for x in rs.fastdesc()]
     ([5, 4, 3, 2, 0], [5, 4, 3, 2, 0])
     >>> assert rs._asclist
 
     iterate ascending without fastasc:
     >>> rs = addset(xs, generatorset(ys), ascending=True)
     >>> assert rs.fastasc is None
     >>> [x for x in rs]
     [0, 2, 3, 4, 5]
 
     iterate descending without fastdesc:
     >>> rs = addset(generatorset(xs), ys, ascending=False)
     >>> assert rs.fastdesc is None
     >>> [x for x in rs]
     [5, 4, 3, 2, 0]
     """
     def __init__(self, revs1, revs2, ascending=None):
         self._r1 = revs1
         self._r2 = revs2
         self._iter = None
         self._ascending = ascending
         self._genlist = None
         self._asclist = None
 
     def __len__(self):
         return len(self._list)
 
     def __nonzero__(self):
         return bool(self._r1) or bool(self._r2)
 
     @util.propertycache
     def _list(self):
         if not self._genlist:
             self._genlist = baseset(iter(self))
         return self._genlist
 
     def __iter__(self):
         """Iterate over both collections without repeating elements
 
         If the ascending attribute is not set, iterate over the first one and
         then over the second one checking for membership on the first one so we
         dont yield any duplicates.
 
         If the ascending attribute is set, iterate over both collections at the
         same time, yielding only one value at a time in the given order.
         """
         if self._ascending is None:
             if self._genlist:
                 return iter(self._genlist)
             def arbitraryordergen():
                 for r in self._r1:
                     yield r
                 inr1 = self._r1.__contains__
                 for r in self._r2:
                     if not inr1(r):
                         yield r
             return arbitraryordergen()
         # try to use our own fast iterator if it exists
         self._trysetasclist()
         if self._ascending:
             attr = 'fastasc'
         else:
             attr = 'fastdesc'
         it = getattr(self, attr)
         if it is not None:
             return it()
         # maybe half of the component supports fast
         # get iterator for _r1
         iter1 = getattr(self._r1, attr)
         if iter1 is None:
             # let's avoid side effect (not sure it matters)
             iter1 = iter(sorted(self._r1, reverse=not self._ascending))
         else:
             iter1 = iter1()
         # get iterator for _r2
         iter2 = getattr(self._r2, attr)
         if iter2 is None:
             # let's avoid side effect (not sure it matters)
             iter2 = iter(sorted(self._r2, reverse=not self._ascending))
         else:
             iter2 = iter2()
         return _iterordered(self._ascending, iter1, iter2)
 
     def _trysetasclist(self):
         """populate the _asclist attribute if possible and necessary"""
         if self._genlist is not None and self._asclist is None:
             self._asclist = sorted(self._genlist)
 
     @property
     def fastasc(self):
         self._trysetasclist()
         if self._asclist is not None:
             return self._asclist.__iter__
         iter1 = self._r1.fastasc
         iter2 = self._r2.fastasc
         if None in (iter1, iter2):
             return None
         return lambda: _iterordered(True, iter1(), iter2())
 
     @property
     def fastdesc(self):
         self._trysetasclist()
         if self._asclist is not None:
             return self._asclist.__reversed__
         iter1 = self._r1.fastdesc
         iter2 = self._r2.fastdesc
         if None in (iter1, iter2):
             return None
         return lambda: _iterordered(False, iter1(), iter2())
 
     def __contains__(self, x):
         return x in self._r1 or x in self._r2
 
     def sort(self, reverse=False):
         """Sort the added set
 
         For this we use the cached list with all the generated values and if we
         know they are ascending or descending we can sort them in a smart way.
         """
         self._ascending = not reverse
 
     def isascending(self):
         return self._ascending is not None and self._ascending
 
     def isdescending(self):
         return self._ascending is not None and not self._ascending
 
     def reverse(self):
         if self._ascending is None:
             self._list.reverse()
         else:
             self._ascending = not self._ascending
 
     def first(self):
         for x in self:
             return x
         return None
 
     def last(self):
         self.reverse()
         val = self.first()
         self.reverse()
         return val
 
     def __repr__(self):
         d = {None: '', False: '-', True: '+'}[self._ascending]
         return '<%s%s %r, %r>' % (type(self).__name__, d, self._r1, self._r2)
 
 class generatorset(abstractsmartset):
     """Wrap a generator for lazy iteration
 
     Wrapper structure for generators that provides lazy membership and can
     be iterated more than once.
     When asked for membership it generates values until either it finds the
     requested one or has gone through all the elements in the generator
     """
     def __init__(self, gen, iterasc=None):
         """
         gen: a generator producing the values for the generatorset.
         """
         self._gen = gen
         self._asclist = None
         self._cache = {}
         self._genlist = []
         self._finished = False
         self._ascending = True
         if iterasc is not None:
             if iterasc:
                 self.fastasc = self._iterator
                 self.__contains__ = self._asccontains
             else:
                 self.fastdesc = self._iterator
                 self.__contains__ = self._desccontains
 
     def __nonzero__(self):
         # Do not use 'for r in self' because it will enforce the iteration
         # order (default ascending), possibly unrolling a whole descending
         # iterator.
         if self._genlist:
             return True
         for r in self._consumegen():
             return True
         return False
 
     def __contains__(self, x):
         if x in self._cache:
             return self._cache[x]
 
         # Use new values only, as existing values would be cached.
         for l in self._consumegen():
             if l == x:
                 return True
 
         self._cache[x] = False
         return False
 
     def _asccontains(self, x):
         """version of contains optimised for ascending generator"""
         if x in self._cache:
             return self._cache[x]
 
         # Use new values only, as existing values would be cached.
         for l in self._consumegen():
             if l == x:
                 return True
             if l > x:
                 break
 
         self._cache[x] = False
         return False
 
     def _desccontains(self, x):
         """version of contains optimised for descending generator"""
         if x in self._cache:
             return self._cache[x]
 
         # Use new values only, as existing values would be cached.
         for l in self._consumegen():
             if l == x:
                 return True
             if l < x:
                 break
 
         self._cache[x] = False
         return False
 
     def __iter__(self):
         if self._ascending:
             it = self.fastasc
         else:
             it = self.fastdesc
         if it is not None:
             return it()
         # we need to consume the iterator
         for x in self._consumegen():
             pass
         # recall the same code
         return iter(self)
 
     def _iterator(self):
         if self._finished:
             return iter(self._genlist)
 
         # We have to use this complex iteration strategy to allow multiple
         # iterations at the same time. We need to be able to catch revision
         # removed from _consumegen and added to genlist in another instance.
         #
         # Getting rid of it would provide an about 15% speed up on this
         # iteration.
         genlist = self._genlist
         nextrev = self._consumegen().next
         _len = len # cache global lookup
         def gen():
             i = 0
             while True:
                 if i < _len(genlist):
                     yield genlist[i]
                 else:
                     yield nextrev()
                 i += 1
         return gen()
 
     def _consumegen(self):
         cache = self._cache
         genlist = self._genlist.append
         for item in self._gen:
             cache[item] = True
             genlist(item)
             yield item
         if not self._finished:
             self._finished = True
             asc = self._genlist[:]
             asc.sort()
             self._asclist = asc
             self.fastasc = asc.__iter__
             self.fastdesc = asc.__reversed__
 
     def __len__(self):
         for x in self._consumegen():
             pass
         return len(self._genlist)
 
     def sort(self, reverse=False):
         self._ascending = not reverse
 
     def reverse(self):
         self._ascending = not self._ascending
 
     def isascending(self):
         return self._ascending
 
     def isdescending(self):
         return not self._ascending
 
     def first(self):
         if self._ascending:
             it = self.fastasc
         else:
             it = self.fastdesc
         if it is None:
             # we need to consume all and try again
             for x in self._consumegen():
                 pass
             return self.first()
         return next(it(), None)
 
     def last(self):
         if self._ascending:
             it = self.fastdesc
         else:
             it = self.fastasc
         if it is None:
             # we need to consume all and try again
             for x in self._consumegen():
                 pass
             return self.first()
         return next(it(), None)
 
     def __repr__(self):
         d = {False: '-', True: '+'}[self._ascending]
         return '<%s%s>' % (type(self).__name__, d)
 
 class spanset(abstractsmartset):
     """Duck type for baseset class which represents a range of revisions and
     can work lazily and without having all the range in memory
 
     Note that spanset(x, y) behave almost like xrange(x, y) except for two
     notable points:
     - when x < y it will be automatically descending,
     - revision filtered with this repoview will be skipped.
 
     """
     def __init__(self, repo, start=0, end=None):
         """
         start: first revision included the set
                (default to 0)
         end:   first revision excluded (last+1)
                (default to len(repo)
 
         Spanset will be descending if `end` < `start`.
         """
         if end is None:
             end = len(repo)
         self._ascending = start <= end
         if not self._ascending:
             start, end = end + 1, start +1
         self._start = start
         self._end = end
         self._hiddenrevs = repo.changelog.filteredrevs
 
     def sort(self, reverse=False):
         self._ascending = not reverse
 
     def reverse(self):
         self._ascending = not self._ascending
 
     def _iterfilter(self, iterrange):
         s = self._hiddenrevs
         for r in iterrange:
             if r not in s:
                 yield r
 
     def __iter__(self):
         if self._ascending:
             return self.fastasc()
         else:
             return self.fastdesc()
 
     def fastasc(self):
         iterrange = xrange(self._start, self._end)
         if self._hiddenrevs:
             return self._iterfilter(iterrange)
         return iter(iterrange)
 
     def fastdesc(self):
         iterrange = xrange(self._end - 1, self._start - 1, -1)
         if self._hiddenrevs:
             return self._iterfilter(iterrange)
         return iter(iterrange)
 
     def __contains__(self, rev):
         hidden = self._hiddenrevs
         return ((self._start <= rev < self._end)
                 and not (hidden and rev in hidden))
 
     def __nonzero__(self):
         for r in self:
             return True
         return False
 
     def __len__(self):
         if not self._hiddenrevs:
             return abs(self._end - self._start)
         else:
             count = 0
             start = self._start
             end = self._end
             for rev in self._hiddenrevs:
                 if (end < rev <= start) or (start <= rev < end):
                     count += 1
             return abs(self._end - self._start) - count
 
     def isascending(self):
         return self._ascending
 
     def isdescending(self):
         return not self._ascending
 
     def first(self):
         if self._ascending:
             it = self.fastasc
         else:
             it = self.fastdesc
         for x in it():
             return x
         return None
 
     def last(self):
         if self._ascending:
             it = self.fastdesc
         else:
             it = self.fastasc
         for x in it():
             return x
         return None
 
     def __repr__(self):
         d = {False: '-', True: '+'}[self._ascending]
         return '<%s%s %d:%d>' % (type(self).__name__, d,
                                  self._start, self._end - 1)
 
 class fullreposet(spanset):
     """a set containing all revisions in the repo
 
     This class exists to host special optimization and magic to handle virtual
     revisions such as "null".
     """
 
     def __init__(self, repo):
         super(fullreposet, self).__init__(repo)
 
     def __and__(self, other):
         """As self contains the whole repo, all of the other set should also be
         in self. Therefore `self & other = other`.
 
         This boldly assumes the other contains valid revs only.
         """
         # other not a smartset, make is so
         if not util.safehasattr(other, 'isascending'):
             # filter out hidden revision
             # (this boldly assumes all smartset are pure)
             #
             # `other` was used with "&", let's assume this is a set like
             # object.
             other = baseset(other - self._hiddenrevs)
 
         # XXX As fullreposet is also used as bootstrap, this is wrong.
         #
         # With a giveme312() revset returning [3,1,2], this makes
         #   'hg log -r "giveme312()"' -> 1, 2, 3 (wrong)
         # We cannot just drop it because other usage still need to sort it:
         #   'hg log -r "all() and giveme312()"' -> 1, 2, 3 (right)
         #
         # There is also some faulty revset implementations that rely on it
         # (eg: children as of its state in e8075329c5fb)
         #
         # When we fix the two points above we can move this into the if clause
         other.sort(reverse=self.isdescending())
         return other
 
 def prettyformatset(revs):
     lines = []
     rs = repr(revs)
     p = 0
     while p < len(rs):
         q = rs.find('<', p + 1)
         if q < 0:
             q = len(rs)
         l = rs.count('<', 0, p) - rs.count('>', 0, p)
         assert l >= 0
         lines.append((l, rs[p:q].rstrip()))
         p = q
     return '\n'.join('  ' * l + s for l, s in lines)
 
 def loadpredicate(ui, extname, registrarobj):
     """Load revset predicates from specified registrarobj
     """
     for name, func in registrarobj._table.iteritems():
         symbols[name] = func
         if func._safe:
             safesymbols.add(name)
 
 # load built-in predicates explicitly to setup safesymbols
 loadpredicate(None, None, predicate)
 
 # tell hggettext to extract docstrings from these functions:
 i18nfunctions = symbols.values()