diff --git a/mercurial/revset.py b/mercurial/revset.py
new file mode 100644
--- /dev/null
+++ b/mercurial/revset.py
@@ -0,0 +1,530 @@
+# revset.py - revision set queries for mercurial
+#
+# Copyright 2010 Matt Mackall <mpm@selenic.com>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+import re
+import parser, util, hg
+import match as _match
+
+elements = {
+    "(": (20, ("group", 1, ")"), ("func", 1, ")")),
+    "-": (19, ("negate", 19), ("minus", 19)),
+    "..": (17, None, ("dagrange", 17)),
+    ":": (15, None, ("range", 15)),
+    "not": (10, ("not", 10)),
+    "!": (10, ("not", 10)),
+    "and": (5, None, ("and", 5)),
+    "&": (5, None, ("and", 5)),
+    "or": (4, None, ("or", 4)),
+    "|": (4, None, ("or", 4)),
+    "+": (4, None, ("or", 4)),
+    ",": (2, None, ("list", 2)),
+    ")": (0, None, None),
+    "symbol": (0, ("symbol",), None),
+    "string": (0, ("string",), None),
+    "end": (0, None, None),
+}
+
+keywords = set(['and', 'or', 'not'])
+
+def tokenize(program):
+    pos, l = 0, len(program)
+    while pos < l:
+        c = program[pos]
+        if c.isspace(): # skip inter-token whitespace
+            pass
+        elif c in "():,-|&+!": # handle simple operators
+            yield (c, None)
+        elif c == '.' and program[pos:pos + 2] == '..': # look ahead carefully
+            yield ('..', None)
+            pos += 1 # skip ahead
+        elif c in '"\'': # handle quoted strings
+            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', program[s:pos].decode('string-escape'))
+                    break
+                pos += 1
+            else:
+                raise "unterminated string"
+        elif c.isalnum() or c in '.': # gather up a symbol/keyword
+            s = pos
+            pos += 1
+            while pos < l: # find end of symbol
+                d = program[pos]
+                if not (d.isalnum() or d in "._"):
+                    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)
+            else:
+                yield ('symbol', sym)
+            pos -= 1
+        else:
+            raise "syntax error at %d" % pos
+        pos += 1
+    yield ('end', None)
+
+# helpers
+
+def getstring(x, err):
+    if x[0] == 'string' or x[0] == 'symbol':
+        return x[1]
+    raise err
+
+def getlist(x):
+    if not x:
+        return []
+    if x[0] == 'list':
+        return getlist(x[1]) + [x[2]]
+    return [x]
+
+def getpair(x, err):
+    l = getlist(x)
+    if len(l) != 2:
+        raise err
+    return l
+
+def getset(repo, subset, x):
+    if not x:
+        raise "missing argument"
+    return methods[x[0]](repo, subset, *x[1:])
+
+# operator methods
+
+def negate(repo, subset, x):
+    return getset(repo, subset,
+                  ('string', '-' + getstring(x, "can't negate that")))
+
+def stringset(repo, subset, x):
+    x = repo[x].rev()
+    if x in subset:
+        return [x]
+    return []
+
+def symbolset(repo, subset, x):
+    if x in symbols:
+        raise "can't use %s here" % x
+    return stringset(repo, subset, x)
+
+def rangeset(repo, subset, x, y):
+    m = getset(repo, subset, x)[0]
+    n = getset(repo, subset, y)[-1]
+    if m < n:
+        return range(m, n + 1)
+    return range(m, n - 1, -1)
+
+def dagrangeset(repo, subset, x, y):
+    return andset(repo, subset,
+                  ('func', ('symbol', 'descendants'), x),
+                  ('func', ('symbol', 'ancestors'), y))
+
+def andset(repo, subset, x, y):
+    if weight(x, True) > weight(y, True):
+        x, y = y, x
+    return getset(repo, getset(repo, subset, x), y)
+
+def orset(repo, subset, x, y):
+    if weight(y, False) < weight(x, False):
+        x, y = y, x
+    s = set(getset(repo, subset, x))
+    s |= set(getset(repo, [r for r in subset if r not in s], y))
+    return [r for r in subset if r in s]
+
+def notset(repo, subset, x):
+    s = set(getset(repo, subset, x))
+    return [r for r in subset if r not in s]
+
+def minusset(repo, subset, x, y):
+    if weight(x, True) > weight(y, True):
+        return getset(repo, notset(repo, subset, y), x)
+    return notset(repo, getset(repo, subset, x), y)
+
+def listset(repo, subset, a, b):
+    raise "can't use a list 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)
+    raise "that's not a function: %s" % a[1]
+
+# functions
+
+def p1(repo, subset, x):
+    ps = set()
+    cl = repo.changelog
+    for r in getset(repo, subset, x):
+        ps.add(cl.parentrevs(r)[0])
+    return [r for r in subset if r in ps]
+
+def p2(repo, subset, x):
+    ps = set()
+    cl = repo.changelog
+    for r in getset(repo, subset, x):
+        ps.add(cl.parentrevs(r)[1])
+    return [r for r in subset if r in ps]
+
+def parents(repo, subset, x):
+    ps = set()
+    cl = repo.changelog
+    for r in getset(repo, subset, x):
+        ps.update(cl.parentrevs(r))
+    return [r for r in subset if r in ps]
+
+def maxrev(repo, subset, x):
+    s = getset(repo, subset, x)
+    if s:
+        m = max(s)
+        if m in subset:
+            return [m]
+    return []
+
+def limit(repo, subset, x):
+    l = getpair(x, "limit wants two args")
+    try:
+        lim = int(getstring(l[1], "limit wants a number"))
+    except ValueError:
+        raise "wants a number"
+    return getset(repo, subset, l[0])[:lim]
+
+def children(repo, subset, x):
+    cs = set()
+    cl = repo.changelog
+    s = set(getset(repo, subset, x))
+    for r in xrange(0, len(repo)):
+        for p in cl.parentrevs(r):
+            if p in s:
+                cs.add(r)
+    return [r for r in subset if r in cs]
+
+def branch(repo, subset, x):
+    s = getset(repo, range(len(repo)), x)
+    b = set()
+    for r in s:
+        b.add(repo[r].branch())
+    s = set(s)
+    return [r for r in subset if r in s or repo[r].branch() in b]
+
+def ancestor(repo, subset, x):
+    l = getpair(x, "ancestor wants two args")
+    a = getset(repo, subset, l[0])
+    b = getset(repo, subset, l[1])
+    if len(a) > 1 or len(b) > 1:
+        raise "arguments to ancestor must be single revisions"
+    return [repo[a[0]].ancestor(repo[b[0]]).rev()]
+
+def ancestors(repo, subset, x):
+    args = getset(repo, range(len(repo)), x)
+    s = set(repo.changelog.ancestors(*args)) | set(args)
+    return [r for r in subset if r in s]
+
+def descendants(repo, subset, x):
+    args = getset(repo, range(len(repo)), x)
+    s = set(repo.changelog.descendants(*args)) | set(args)
+    return [r for r in subset if r in s]
+
+def follow(repo, subset, x):
+    if x:
+        raise "follow takes no args"
+    p = repo['.'].rev()
+    s = set(repo.changelog.ancestors(p)) | set([p])
+    return [r for r in subset if r in s]
+
+def date(repo, subset, x):
+    ds = getstring(x, 'date wants a string')
+    dm = util.matchdate(ds)
+    return [r for r in subset if dm(repo[r].date()[0])]
+
+def keyword(repo, subset, x):
+    kw = getstring(x, "keyword wants a string").lower()
+    l = []
+    for r in subset:
+        c = repo[r]
+        t = " ".join(c.files() + [c.user(), c.description()])
+        if kw in t.lower():
+            l.append(r)
+    return l
+
+def grep(repo, subset, x):
+    gr = re.compile(getstring(x, "grep wants a string"))
+    l = []
+    for r in subset:
+        c = repo[r]
+        for e in c.files() + [c.user(), c.description()]:
+            if gr.search(e):
+                l.append(r)
+                continue
+    return l
+
+def author(repo, subset, x):
+    n = getstring(x, "author wants a string").lower()
+    return [r for r in subset if n in repo[r].user().lower()]
+
+def hasfile(repo, subset, x):
+    pat = getstring(x, "file wants a pattern")
+    m = _match.match(repo.root, repo.getcwd(), [pat])
+    s = []
+    for r in subset:
+        for f in repo[r].files():
+            if m(f):
+                s.append(r)
+                continue
+    return s
+
+def contains(repo, subset, x):
+    pat = getstring(x, "file wants a pattern")
+    m = _match.match(repo.root, repo.getcwd(), [pat])
+    s = []
+    if m.files() == [pat]:
+        for r in subset:
+            if pat in repo[r]:
+                s.append(r)
+                continue
+    else:
+        for r in subset:
+            c = repo[r]
+            for f in repo[r].manifest():
+                if m(f):
+                    s.append(r)
+                    continue
+    return s
+
+def checkstatus(repo, subset, pat, field):
+    m = _match.match(repo.root, repo.getcwd(), [pat])
+    s = []
+    fast = (m.files() == [pat])
+    for r in subset:
+        c = repo[r]
+        if fast:
+            if pat not in c.files():
+                continue
+        else:
+            for f in c.files():
+                if m(f):
+                    break
+            else:
+                continue
+        files = repo.status(c.p1().node(), c.node())[field]
+        if fast:
+            if pat in files:
+                s.append(r)
+                continue
+        else:
+            for f in files:
+                if m(f):
+                    s.append(r)
+                    continue
+    return s
+
+def modifies(repo, subset, x):
+    pat = getstring(x, "modifies wants a pattern")
+    return checkstatus(repo, subset, pat, 0)
+
+def adds(repo, subset, x):
+    pat = getstring(x, "adds wants a pattern")
+    return checkstatus(repo, subset, pat, 1)
+
+def removes(repo, subset, x):
+    pat = getstring(x, "removes wants a pattern")
+    return checkstatus(repo, subset, pat, 2)
+
+def merge(repo, subset, x):
+    if x:
+        raise "merge takes no args"
+    cl = repo.changelog
+    return [r for r in subset if cl.parentrevs(r)[1] != -1]
+
+def closed(repo, subset, x):
+    return [r for r in subset if repo[r].extra('close')]
+
+def head(repo, subset, x):
+    hs = set()
+    for b, ls in repo.branchmap().iteritems():
+        hs.update(repo[h].rev() for h in ls)
+    return [r for r in subset if r in hs]
+
+def reverse(repo, subset, x):
+    l = getset(repo, subset, x)
+    l.reverse()
+    return l
+
+def sort(repo, subset, x):
+    l = getlist(x)
+    keys = "rev"
+    if len(l) == 2:
+        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)
+    for r in getset(repo, subset, s):
+        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 "unknown sort key %r" % k
+        e.append(r)
+        l.append(e)
+    l.sort()
+    return [e[-1] for e in l]
+
+def getall(repo, subset, x):
+    return subset
+
+def heads(repo, subset, x):
+    s = getset(repo, subset, x)
+    ps = set(parents(repo, subset, x))
+    return [r for r in s if r not in ps]
+
+def roots(repo, subset, x):
+    s = getset(repo, subset, x)
+    cs = set(children(repo, subset, x))
+    return [r for r in s if r not in cs]
+
+def outgoing(repo, subset, x):
+    l = getlist(x)
+    if len(l) == 1:
+        dest = getstring(l[0], "outgoing wants a repo path")
+    else:
+        dest = ''
+    dest = repo.ui.expandpath(dest or 'default-push', dest or 'default')
+    dest, branches = hg.parseurl(dest)
+    other = hg.repository(hg.remoteui(repo, {}), dest)
+    repo.ui.pushbuffer()
+    o = repo.findoutgoing(other)
+    repo.ui.popbuffer()
+    cl = repo.changelog
+    o = set([cl.rev(r) for r in repo.changelog.nodesbetween(o, None)[0]])
+    print 'out', dest, o
+    return [r for r in subset if r in o]
+
+symbols = {
+    "ancestor": ancestor,
+    "ancestors": ancestors,
+    "descendants": descendants,
+    "follow": follow,
+    "merge": merge,
+    "reverse": reverse,
+    "sort": sort,
+    "branch": branch,
+    "keyword": keyword,
+    "author": author,
+    "user": author,
+    "date": date,
+    "grep": grep,
+    "p1": p1,
+    "p2": p2,
+    "parents": parents,
+    "children": children,
+    "max": maxrev,
+    "limit": limit,
+    "file": hasfile,
+    "contains": contains,
+    "heads": heads,
+    "roots": roots,
+    "all": getall,
+    "closed": closed,
+    "head": head,
+    "modifies": modifies,
+    "adds": adds,
+    "removes": removes,
+    "outgoing": outgoing,
+}
+
+methods = {
+    "negate": negate,
+    "minus": minusset,
+    "range": rangeset,
+    "dagrange": dagrangeset,
+    "string": stringset,
+    "symbol": symbolset,
+    "and": andset,
+    "or": orset,
+    "not": notset,
+    "list": listset,
+    "func": func,
+    "group": lambda r, s, x: getset(r, s, x),
+}
+
+def weight(x, small):
+    smallbonus = 1
+    if small:
+        smallbonus = .5
+
+    op = x[0]
+    if op in 'string symbol negate':
+        return smallbonus # single revisions are small
+    elif op == 'and' or op == 'dagrange':
+        return min(weight(x[1], True), weight(x[2], True))
+    elif op in 'or -':
+        return max(weight(x[1], False), weight(x[2], False))
+    elif op == 'not':
+        return weight(x[1], not small)
+    elif op == 'group':
+        return weight(x[1], small)
+    elif op == 'range':
+        return weight(x[1], small) + weight(x[2], small)
+    elif op == 'func':
+        f = getstring(x[1], "not a symbol")
+        if f in "grep date user author keyword branch file":
+            return 10 # slow
+        elif f in "modifies adds removes":
+            return 30 # slower
+        elif f == "contains":
+            return 100 # very slow
+        elif f == "ancestor":
+            return (weight(x[1][1], small) +
+                    weight(x[1][2], small)) * smallbonus
+        elif f == "reverse limit":
+            return weight(x[1], small)
+        elif f in "sort":
+            base = x[1]
+            spec = "rev"
+            if x[1][0] == 'list':
+                base = x[1][1]
+                spec = x[1][2]
+            return max(weight(base, small), 10)
+        else:
+            return 1
+
+parse = parser.parser(tokenize, elements).parse
+
+def match(spec):
+    tree = parse(spec)
+    def mfunc(repo, subset):
+        return getset(repo, subset, tree)
+    return mfunc