match: make subinclude construction lazy

The matcher subinclude functionality allows us to have .hgignore files that
include subdirectory hgignore files. Today it parses the entire repo at once,
even if we only need to test a file in one subdirectory. This patch makes the
subinclude tree creation lazy, which speeds up matcher creation significantly in
large repos with very large trees of ignore patterns.

mercurial/match.py

@@ -1,788 +1,795 b''
 # match.py - filename matching
 #
 #  Copyright 2008, 2009 Matt Mackall <[e-mail]> and others
 #
 # 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 copy
 import os
 import re
 
 from .i18n import _
 from . import (
     error,
     pathutil,
     util,
 )
 
 propertycache = util.propertycache
 
 def _rematcher(regex):
     '''compile the regexp with the best available regexp engine and return a
     matcher function'''
     m = util.re.compile(regex)
     try:
         # slightly faster, provided by facebook's re2 bindings
         return m.test_match
     except AttributeError:
         return m.match
 
 def _expandsets(kindpats, ctx, listsubrepos):
     '''Returns the kindpats list with the 'set' patterns expanded.'''
     fset = set()
     other = []
 
     for kind, pat, source in kindpats:
         if kind == 'set':
             if not ctx:
                 raise error.Abort(_("fileset expression with no context"))
             s = ctx.getfileset(pat)
             fset.update(s)
 
             if listsubrepos:
                 for subpath in ctx.substate:
                     s = ctx.sub(subpath).getfileset(pat)
                     fset.update(subpath + '/' + f for f in s)
 
             continue
         other.append((kind, pat, source))
     return fset, other
 
 def _expandsubinclude(kindpats, root):
-    '''Returns the list of subinclude matchers and the kindpats without the
+    '''Returns the list of subinclude matcher args and the kindpats without the
     subincludes in it.'''
     relmatchers = []
     other = []
 
     for kind, pat, source in kindpats:
         if kind == 'subinclude':
             sourceroot = pathutil.dirname(util.normpath(source))
             pat = util.pconvert(pat)
             path = pathutil.join(sourceroot, pat)
 
             newroot = pathutil.dirname(path)
-            relmatcher = match(newroot, '', [], ['include:%s' % path])
+            matcherargs = (newroot, '', [], ['include:%s' % path])
 
             prefix = pathutil.canonpath(root, root, newroot)
             if prefix:
                 prefix += '/'
-            relmatchers.append((prefix, relmatcher))
+            relmatchers.append((prefix, matcherargs))
         else:
             other.append((kind, pat, source))
 
     return relmatchers, other
 
 def _kindpatsalwaysmatch(kindpats):
     """"Checks whether the kindspats match everything, as e.g.
     'relpath:.' does.
     """
     for kind, pat, source in kindpats:
         if pat != '' or kind not in ['relpath', 'glob']:
             return False
     return True
 
 class match(object):
     def __init__(self, root, cwd, patterns, include=None, exclude=None,
                  default='glob', exact=False, auditor=None, ctx=None,
                  listsubrepos=False, warn=None, badfn=None):
         """build an object to match a set of file patterns
 
         arguments:
         root - the canonical root of the tree you're matching against
         cwd - the current working directory, if relevant
         patterns - patterns to find
         include - patterns to include (unless they are excluded)
         exclude - patterns to exclude (even if they are included)
         default - if a pattern in patterns has no explicit type, assume this one
         exact - patterns are actually filenames (include/exclude still apply)
         warn - optional function used for printing warnings
         badfn - optional bad() callback for this matcher instead of the default
 
         a pattern is one of:
         'glob:<glob>' - a glob relative to cwd
         're:<regexp>' - a regular expression
         'path:<path>' - a path relative to repository root, which is matched
                         recursively
         'rootfilesin:<path>' - a path relative to repository root, which is
                         matched non-recursively (will not match subdirectories)
         'relglob:<glob>' - an unrooted glob (*.c matches C files in all dirs)
         'relpath:<path>' - a path relative to cwd
         'relre:<regexp>' - a regexp that needn't match the start of a name
         'set:<fileset>' - a fileset expression
         'include:<path>' - a file of patterns to read and include
         'subinclude:<path>' - a file of patterns to match against files under
                               the same directory
         '<something>' - a pattern of the specified default type
         """
         if include is None:
             include = []
         if exclude is None:
             exclude = []
 
         self._root = root
         self._cwd = cwd
         self._files = [] # exact files and roots of patterns
         self._anypats = bool(include or exclude)
         self._always = False
         self._pathrestricted = bool(include or exclude or patterns)
         self._warn = warn
 
         # roots are directories which are recursively included/excluded.
         self._includeroots = set()
         self._excluderoots = set()
         # dirs are directories which are non-recursively included.
         self._includedirs = set(['.'])
 
         if badfn is not None:
             self.bad = badfn
 
         matchfns = []
         if include:
             kindpats = self._normalize(include, 'glob', root, cwd, auditor)
             self.includepat, im = _buildmatch(ctx, kindpats, '(?:/|$)',
                                               listsubrepos, root)
             roots, dirs = _rootsanddirs(kindpats)
             self._includeroots.update(roots)
             self._includedirs.update(dirs)
             matchfns.append(im)
         if exclude:
             kindpats = self._normalize(exclude, 'glob', root, cwd, auditor)
             self.excludepat, em = _buildmatch(ctx, kindpats, '(?:/|$)',
                                               listsubrepos, root)
             if not _anypats(kindpats):
                 # Only consider recursive excludes as such - if a non-recursive
                 # exclude is used, we must still recurse into the excluded
                 # directory, at least to find subdirectories. In such a case,
                 # the regex still won't match the non-recursively-excluded
                 # files.
                 self._excluderoots.update(_roots(kindpats))
             matchfns.append(lambda f: not em(f))
         if exact:
             if isinstance(patterns, list):
                 self._files = patterns
             else:
                 self._files = list(patterns)
             matchfns.append(self.exact)
         elif patterns:
             kindpats = self._normalize(patterns, default, root, cwd, auditor)
             if not _kindpatsalwaysmatch(kindpats):
                 self._files = _explicitfiles(kindpats)
                 self._anypats = self._anypats or _anypats(kindpats)
                 self.patternspat, pm = _buildmatch(ctx, kindpats, '$',
                                                    listsubrepos, root)
                 matchfns.append(pm)
 
         if not matchfns:
             m = util.always
             self._always = True
         elif len(matchfns) == 1:
             m = matchfns[0]
         else:
             def m(f):
                 for matchfn in matchfns:
                     if not matchfn(f):
                         return False
                 return True
 
         self.matchfn = m
         self._fileroots = set(self._files)
 
     def __call__(self, fn):
         return self.matchfn(fn)
     def __iter__(self):
         for f in self._files:
             yield f
 
     # Callbacks related to how the matcher is used by dirstate.walk.
     # Subscribers to these events must monkeypatch the matcher object.
     def bad(self, f, msg):
         '''Callback from dirstate.walk for each explicit file that can't be
         found/accessed, with an error message.'''
         pass
 
     # If an explicitdir is set, it will be called when an explicitly listed
     # directory is visited.
     explicitdir = None
 
     # If an traversedir is set, it will be called when a directory discovered
     # by recursive traversal is visited.
     traversedir = None
 
     def abs(self, f):
         '''Convert a repo path back to path that is relative to the root of the
         matcher.'''
         return f
 
     def rel(self, f):
         '''Convert repo path back to path that is relative to cwd of matcher.'''
         return util.pathto(self._root, self._cwd, f)
 
     def uipath(self, f):
         '''Convert repo path to a display path.  If patterns or -I/-X were used
         to create this matcher, the display path will be relative to cwd.
         Otherwise it is relative to the root of the repo.'''
         return (self._pathrestricted and self.rel(f)) or self.abs(f)
 
     def files(self):
         '''Explicitly listed files or patterns or roots:
         if no patterns or .always(): empty list,
         if exact: list exact files,
         if not .anypats(): list all files and dirs,
         else: optimal roots'''
         return self._files
 
     @propertycache
     def _dirs(self):
         return set(util.dirs(self._fileroots)) | set(['.'])
 
     def visitdir(self, dir):
         '''Decides whether a directory should be visited based on whether it
         has potential matches in it or one of its subdirectories. This is
         based on the match's primary, included, and excluded patterns.
 
         Returns the string 'all' if the given directory and all subdirectories
         should be visited. Otherwise returns True or False indicating whether
         the given directory should be visited.
 
         This function's behavior is undefined if it has returned False for
         one of the dir's parent directories.
         '''
         if self.prefix() and dir in self._fileroots:
             return 'all'
         if dir in self._excluderoots:
             return False
         if ((self._includeroots or self._includedirs != set(['.'])) and
             '.' not in self._includeroots and
             dir not in self._includeroots and
             dir not in self._includedirs and
             not any(parent in self._includeroots
                     for parent in util.finddirs(dir))):
             return False
         return (not self._fileroots or
                 '.' in self._fileroots or
                 dir in self._fileroots or
                 dir in self._dirs or
                 any(parentdir in self._fileroots
                     for parentdir in util.finddirs(dir)))
 
     def exact(self, f):
         '''Returns True if f is in .files().'''
         return f in self._fileroots
 
     def anypats(self):
         '''Matcher uses patterns or include/exclude.'''
         return self._anypats
 
     def always(self):
         '''Matcher will match everything and .files() will be empty
         - optimization might be possible and necessary.'''
         return self._always
 
     def ispartial(self):
         '''True if the matcher won't always match.
 
         Although it's just the inverse of _always in this implementation,
         an extension such as narrowhg might make it return something
         slightly different.'''
         return not self._always
 
     def isexact(self):
         return self.matchfn == self.exact
 
     def prefix(self):
         return not self.always() and not self.isexact() and not self.anypats()
 
     def _normalize(self, patterns, default, root, cwd, auditor):
         '''Convert 'kind:pat' from the patterns list to tuples with kind and
         normalized and rooted patterns and with listfiles expanded.'''
         kindpats = []
         for kind, pat in [_patsplit(p, default) for p in patterns]:
             if kind in ('glob', 'relpath'):
                 pat = pathutil.canonpath(root, cwd, pat, auditor)
             elif kind in ('relglob', 'path', 'rootfilesin'):
                 pat = util.normpath(pat)
             elif kind in ('listfile', 'listfile0'):
                 try:
                     files = util.readfile(pat)
                     if kind == 'listfile0':
                         files = files.split('\0')
                     else:
                         files = files.splitlines()
                     files = [f for f in files if f]
                 except EnvironmentError:
                     raise error.Abort(_("unable to read file list (%s)") % pat)
                 for k, p, source in self._normalize(files, default, root, cwd,
                                                     auditor):
                     kindpats.append((k, p, pat))
                 continue
             elif kind == 'include':
                 try:
                     fullpath = os.path.join(root, util.localpath(pat))
                     includepats = readpatternfile(fullpath, self._warn)
                     for k, p, source in self._normalize(includepats, default,
                                                         root, cwd, auditor):
                         kindpats.append((k, p, source or pat))
                 except error.Abort as inst:
                     raise error.Abort('%s: %s' % (pat, inst[0]))
                 except IOError as inst:
                     if self._warn:
                         self._warn(_("skipping unreadable pattern file "
                                      "'%s': %s\n") % (pat, inst.strerror))
                 continue
             # else: re or relre - which cannot be normalized
             kindpats.append((kind, pat, ''))
         return kindpats
 
 def exact(root, cwd, files, badfn=None):
     return match(root, cwd, files, exact=True, badfn=badfn)
 
 def always(root, cwd):
     return match(root, cwd, [])
 
 def badmatch(match, badfn):
     """Make a copy of the given matcher, replacing its bad method with the given
     one.
     """
     m = copy.copy(match)
     m.bad = badfn
     return m
 
 class subdirmatcher(match):
     """Adapt a matcher to work on a subdirectory only.
 
     The paths are remapped to remove/insert the path as needed:
 
     >>> m1 = match('root', '', ['a.txt', 'sub/b.txt'])
     >>> m2 = subdirmatcher('sub', m1)
     >>> bool(m2('a.txt'))
     False
     >>> bool(m2('b.txt'))
     True
     >>> bool(m2.matchfn('a.txt'))
     False
     >>> bool(m2.matchfn('b.txt'))
     True
     >>> m2.files()
     ['b.txt']
     >>> m2.exact('b.txt')
     True
     >>> util.pconvert(m2.rel('b.txt'))
     'sub/b.txt'
     >>> def bad(f, msg):
     ...     print "%s: %s" % (f, msg)
     >>> m1.bad = bad
     >>> m2.bad('x.txt', 'No such file')
     sub/x.txt: No such file
     >>> m2.abs('c.txt')
     'sub/c.txt'
     """
 
     def __init__(self, path, matcher):
         self._root = matcher._root
         self._cwd = matcher._cwd
         self._path = path
         self._matcher = matcher
         self._always = matcher._always
         self._pathrestricted = matcher._pathrestricted
 
         self._files = [f[len(path) + 1:] for f in matcher._files
                        if f.startswith(path + "/")]
 
         # If the parent repo had a path to this subrepo and no patterns are
         # specified, this submatcher always matches.
         if not self._always and not matcher._anypats:
             self._always = any(f == path for f in matcher._files)
 
         self._anypats = matcher._anypats
         # Some information is lost in the superclass's constructor, so we
         # can not accurately create the matching function for the subdirectory
         # from the inputs. Instead, we override matchfn() and visitdir() to
         # call the original matcher with the subdirectory path prepended.
         self.matchfn = lambda fn: matcher.matchfn(self._path + "/" + fn)
         def visitdir(dir):
             if dir == '.':
                 return matcher.visitdir(self._path)
             return matcher.visitdir(self._path + "/" + dir)
         self.visitdir = visitdir
         self._fileroots = set(self._files)
 
     def abs(self, f):
         return self._matcher.abs(self._path + "/" + f)
 
     def bad(self, f, msg):
         self._matcher.bad(self._path + "/" + f, msg)
 
     def rel(self, f):
         return self._matcher.rel(self._path + "/" + f)
 
 class icasefsmatcher(match):
     """A matcher for wdir on case insensitive filesystems, which normalizes the
     given patterns to the case in the filesystem.
     """
 
     def __init__(self, root, cwd, patterns, include, exclude, default, auditor,
                  ctx, listsubrepos=False, badfn=None):
         init = super(icasefsmatcher, self).__init__
         self._dirstate = ctx.repo().dirstate
         self._dsnormalize = self._dirstate.normalize
 
         init(root, cwd, patterns, include, exclude, default, auditor=auditor,
              ctx=ctx, listsubrepos=listsubrepos, badfn=badfn)
 
         # m.exact(file) must be based off of the actual user input, otherwise
         # inexact case matches are treated as exact, and not noted without -v.
         if self._files:
             roots, dirs = _rootsanddirs(self._kp)
             self._fileroots = set(roots)
             self._fileroots.update(dirs)
 
     def _normalize(self, patterns, default, root, cwd, auditor):
         self._kp = super(icasefsmatcher, self)._normalize(patterns, default,
                                                           root, cwd, auditor)
         kindpats = []
         for kind, pats, source in self._kp:
             if kind not in ('re', 'relre'):  # regex can't be normalized
                 p = pats
                 pats = self._dsnormalize(pats)
 
                 # Preserve the original to handle a case only rename.
                 if p != pats and p in self._dirstate:
                     kindpats.append((kind, p, source))
 
             kindpats.append((kind, pats, source))
         return kindpats
 
 def patkind(pattern, default=None):
     '''If pattern is 'kind:pat' with a known kind, return kind.'''
     return _patsplit(pattern, default)[0]
 
 def _patsplit(pattern, default):
     """Split a string into the optional pattern kind prefix and the actual
     pattern."""
     if ':' in pattern:
         kind, pat = pattern.split(':', 1)
         if kind in ('re', 'glob', 'path', 'relglob', 'relpath', 'relre',
                     'listfile', 'listfile0', 'set', 'include', 'subinclude',
                     'rootfilesin'):
             return kind, pat
     return default, pattern
 
 def _globre(pat):
     r'''Convert an extended glob string to a regexp string.
 
     >>> print _globre(r'?')
     .
     >>> print _globre(r'*')
     [^/]*
     >>> print _globre(r'**')
     .*
     >>> print _globre(r'**/a')
     (?:.*/)?a
     >>> print _globre(r'a/**/b')
     a\/(?:.*/)?b
     >>> print _globre(r'[a*?!^][^b][!c]')
     [a*?!^][\^b][^c]
     >>> print _globre(r'{a,b}')
     (?:a|b)
     >>> print _globre(r'.\*\?')
     \.\*\?
     '''
     i, n = 0, len(pat)
     res = ''
     group = 0
     escape = util.re.escape
     def peek():
         return i < n and pat[i:i + 1]
     while i < n:
         c = pat[i:i + 1]
         i += 1
         if c not in '*?[{},\\':
             res += escape(c)
         elif c == '*':
             if peek() == '*':
                 i += 1
                 if peek() == '/':
                     i += 1
                     res += '(?:.*/)?'
                 else:
                     res += '.*'
             else:
                 res += '[^/]*'
         elif c == '?':
             res += '.'
         elif c == '[':
             j = i
             if j < n and pat[j:j + 1] in '!]':
                 j += 1
             while j < n and pat[j:j + 1] != ']':
                 j += 1
             if j >= n:
                 res += '\\['
             else:
                 stuff = pat[i:j].replace('\\','\\\\')
                 i = j + 1
                 if stuff[0:1] == '!':
                     stuff = '^' + stuff[1:]
                 elif stuff[0:1] == '^':
                     stuff = '\\' + stuff
                 res = '%s[%s]' % (res, stuff)
         elif c == '{':
             group += 1
             res += '(?:'
         elif c == '}' and group:
             res += ')'
             group -= 1
         elif c == ',' and group:
             res += '|'
         elif c == '\\':
             p = peek()
             if p:
                 i += 1
                 res += escape(p)
             else:
                 res += escape(c)
         else:
             res += escape(c)
     return res
 
 def _regex(kind, pat, globsuffix):
     '''Convert a (normalized) pattern of any kind into a regular expression.
     globsuffix is appended to the regexp of globs.'''
     if not pat:
         return ''
     if kind == 're':
         return pat
     if kind == 'path':
         if pat == '.':
             return ''
         return '^' + util.re.escape(pat) + '(?:/|$)'
     if kind == 'rootfilesin':
         if pat == '.':
             escaped = ''
         else:
             # Pattern is a directory name.
             escaped = util.re.escape(pat) + '/'
         # Anything after the pattern must be a non-directory.
         return '^' + escaped + '[^/]+$'
     if kind == 'relglob':
         return '(?:|.*/)' + _globre(pat) + globsuffix
     if kind == 'relpath':
         return util.re.escape(pat) + '(?:/|$)'
     if kind == 'relre':
         if pat.startswith('^'):
             return pat
         return '.*' + pat
     return _globre(pat) + globsuffix
 
 def _buildmatch(ctx, kindpats, globsuffix, listsubrepos, root):
     '''Return regexp string and a matcher function for kindpats.
     globsuffix is appended to the regexp of globs.'''
     matchfuncs = []
 
     subincludes, kindpats = _expandsubinclude(kindpats, root)
     if subincludes:
+        submatchers = {}
         def matchsubinclude(f):
-            for prefix, mf in subincludes:
-                if f.startswith(prefix) and mf(f[len(prefix):]):
+            for prefix, matcherargs in subincludes:
+                if f.startswith(prefix):
+                    mf = submatchers.get(prefix)
+                    if mf is None:
+                        mf = match(*matcherargs)
+                        submatchers[prefix] = mf
+
+                    if mf(f[len(prefix):]):
                     return True
             return False
         matchfuncs.append(matchsubinclude)
 
     fset, kindpats = _expandsets(kindpats, ctx, listsubrepos)
     if fset:
         matchfuncs.append(fset.__contains__)
 
     regex = ''
     if kindpats:
         regex, mf = _buildregexmatch(kindpats, globsuffix)
         matchfuncs.append(mf)
 
     if len(matchfuncs) == 1:
         return regex, matchfuncs[0]
     else:
         return regex, lambda f: any(mf(f) for mf in matchfuncs)
 
 def _buildregexmatch(kindpats, globsuffix):
     """Build a match function from a list of kinds and kindpats,
     return regexp string and a matcher function."""
     try:
         regex = '(?:%s)' % '|'.join([_regex(k, p, globsuffix)
                                      for (k, p, s) in kindpats])
         if len(regex) > 20000:
             raise OverflowError
         return regex, _rematcher(regex)
     except OverflowError:
         # We're using a Python with a tiny regex engine and we
         # made it explode, so we'll divide the pattern list in two
         # until it works
         l = len(kindpats)
         if l < 2:
             raise
         regexa, a = _buildregexmatch(kindpats[:l//2], globsuffix)
         regexb, b = _buildregexmatch(kindpats[l//2:], globsuffix)
         return regex, lambda s: a(s) or b(s)
     except re.error:
         for k, p, s in kindpats:
             try:
                 _rematcher('(?:%s)' % _regex(k, p, globsuffix))
             except re.error:
                 if s:
                     raise error.Abort(_("%s: invalid pattern (%s): %s") %
                                      (s, k, p))
                 else:
                     raise error.Abort(_("invalid pattern (%s): %s") % (k, p))
         raise error.Abort(_("invalid pattern"))
 
 def _patternrootsanddirs(kindpats):
     '''Returns roots and directories corresponding to each pattern.
 
     This calculates the roots and directories exactly matching the patterns and
     returns a tuple of (roots, dirs) for each. It does not return other
     directories which may also need to be considered, like the parent
     directories.
     '''
     r = []
     d = []
     for kind, pat, source in kindpats:
         if kind == 'glob': # find the non-glob prefix
             root = []
             for p in pat.split('/'):
                 if '[' in p or '{' in p or '*' in p or '?' in p:
                     break
                 root.append(p)
             r.append('/'.join(root) or '.')
         elif kind in ('relpath', 'path'):
             r.append(pat or '.')
         elif kind in ('rootfilesin',):
             d.append(pat or '.')
         else: # relglob, re, relre
             r.append('.')
     return r, d
 
 def _roots(kindpats):
     '''Returns root directories to match recursively from the given patterns.'''
     roots, dirs = _patternrootsanddirs(kindpats)
     return roots
 
 def _rootsanddirs(kindpats):
     '''Returns roots and exact directories from patterns.
 
     roots are directories to match recursively, whereas exact directories should
     be matched non-recursively. The returned (roots, dirs) tuple will also
     include directories that need to be implicitly considered as either, such as
     parent directories.
 
     >>> _rootsanddirs(\
         [('glob', 'g/h/*', ''), ('glob', 'g/h', ''), ('glob', 'g*', '')])
     (['g/h', 'g/h', '.'], ['g'])
     >>> _rootsanddirs(\
         [('rootfilesin', 'g/h', ''), ('rootfilesin', '', '')])
     ([], ['g/h', '.', 'g'])
     >>> _rootsanddirs(\
         [('relpath', 'r', ''), ('path', 'p/p', ''), ('path', '', '')])
     (['r', 'p/p', '.'], ['p'])
     >>> _rootsanddirs(\
         [('relglob', 'rg*', ''), ('re', 're/', ''), ('relre', 'rr', '')])
     (['.', '.', '.'], [])
     '''
     r, d = _patternrootsanddirs(kindpats)
 
     # Append the parents as non-recursive/exact directories, since they must be
     # scanned to get to either the roots or the other exact directories.
     d.extend(util.dirs(d))
     d.extend(util.dirs(r))
 
     return r, d
 
 def _explicitfiles(kindpats):
     '''Returns the potential explicit filenames from the patterns.
 
     >>> _explicitfiles([('path', 'foo/bar', '')])
     ['foo/bar']
     >>> _explicitfiles([('rootfilesin', 'foo/bar', '')])
     []
     '''
     # Keep only the pattern kinds where one can specify filenames (vs only
     # directory names).
     filable = [kp for kp in kindpats if kp[0] not in ('rootfilesin',)]
     return _roots(filable)
 
 def _anypats(kindpats):
     for kind, pat, source in kindpats:
         if kind in ('glob', 're', 'relglob', 'relre', 'set', 'rootfilesin'):
             return True
 
 _commentre = None
 
 def readpatternfile(filepath, warn, sourceinfo=False):
     '''parse a pattern file, returning a list of
     patterns. These patterns should be given to compile()
     to be validated and converted into a match function.
 
     trailing white space is dropped.
     the escape character is backslash.
     comments start with #.
     empty lines are skipped.
 
     lines can be of the following formats:
 
     syntax: regexp # defaults following lines to non-rooted regexps
     syntax: glob   # defaults following lines to non-rooted globs
     re:pattern     # non-rooted regular expression
     glob:pattern   # non-rooted glob
     pattern        # pattern of the current default type
 
     if sourceinfo is set, returns a list of tuples:
     (pattern, lineno, originalline). This is useful to debug ignore patterns.
     '''
 
     syntaxes = {'re': 'relre:', 'regexp': 'relre:', 'glob': 'relglob:',
                 'include': 'include', 'subinclude': 'subinclude'}
     syntax = 'relre:'
     patterns = []
 
     fp = open(filepath, 'rb')
     for lineno, line in enumerate(util.iterfile(fp), start=1):
         if "#" in line:
             global _commentre
             if not _commentre:
                 _commentre = util.re.compile(br'((?:^|[^\\])(?:\\\\)*)#.*')
             # remove comments prefixed by an even number of escapes
             m = _commentre.search(line)
             if m:
                 line = line[:m.end(1)]
             # fixup properly escaped comments that survived the above
             line = line.replace("\\#", "#")
         line = line.rstrip()
         if not line:
             continue
 
         if line.startswith('syntax:'):
             s = line[7:].strip()
             try:
                 syntax = syntaxes[s]
             except KeyError:
                 if warn:
                     warn(_("%s: ignoring invalid syntax '%s'\n") %
                          (filepath, s))
             continue
 
         linesyntax = syntax
         for s, rels in syntaxes.iteritems():
             if line.startswith(rels):
                 linesyntax = rels
                 line = line[len(rels):]
                 break
             elif line.startswith(s+':'):
                 linesyntax = rels
                 line = line[len(s) + 1:]
                 break
         if sourceinfo:
             patterns.append((linesyntax + line, lineno, line))
         else:
             patterns.append(linesyntax + line)
     fp.close()
     return patterns