Mercurial > hg
view mercurial/pathutil.py @ 29322:66dbdd3cc2b9 stable
bdiff: extend matches across popular lines
For very large diffs that have large numbers of identical lines (JSON
dumps) that also have large blocks of identical text, bdiff could become
confused about which block matches which because it can only match
very limited regions. The result is very large diffs for small sets of edits.
The earlier recursion rebalancing fix made this behavior more frequent because
it's now more prone to match block 1 to block 2. One frequent user of
large JSON files reported being unable to pass the resulting diffs
through their code review system.
Prior to this change, bdiff would calculate the length of a match at
(i, j) as 1 + length found at (i-1, j-1). With large number of popular
(ignored) lines, this often meant matches couldn't be extended
backwards at all and thus all matching regions were very small.
Disabling the popularity threshold is not an option because it brings
back quadratic behavior.
Instead, we extend a match backwards until we either found a previously
discovered match or we find a mismatching line. This thus successfully
bridges over any popular lines inside and before a matching region.
The larger regions then significant reduce the probability of confusion.
author | Matt Mackall <mpm@selenic.com> |
---|---|
date | Thu, 02 Jun 2016 17:09:06 -0500 |
parents | 0b7ce0b16d8a |
children | 6f447b9ec263 |
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from __future__ import absolute_import import errno import os import posixpath import stat from .i18n import _ from . import ( encoding, error, util, ) def _lowerclean(s): return encoding.hfsignoreclean(s.lower()) class pathauditor(object): '''ensure that a filesystem path contains no banned components. the following properties of a path are checked: - ends with a directory separator - under top-level .hg - starts at the root of a windows drive - contains ".." More check are also done about the file system states: - traverses a symlink (e.g. a/symlink_here/b) - inside a nested repository (a callback can be used to approve some nested repositories, e.g., subrepositories) The file system checks are only done when 'realfs' is set to True (the default). They should be disable then we are auditing path for operation on stored history. ''' def __init__(self, root, callback=None, realfs=True): self.audited = set() self.auditeddir = set() self.root = root self._realfs = realfs self.callback = callback if os.path.lexists(root) and not util.checkcase(root): self.normcase = util.normcase else: self.normcase = lambda x: x def __call__(self, path): '''Check the relative path. path may contain a pattern (e.g. foodir/**.txt)''' path = util.localpath(path) normpath = self.normcase(path) if normpath in self.audited: return # AIX ignores "/" at end of path, others raise EISDIR. if util.endswithsep(path): raise error.Abort(_("path ends in directory separator: %s") % path) parts = util.splitpath(path) if (os.path.splitdrive(path)[0] or _lowerclean(parts[0]) in ('.hg', '.hg.', '') or os.pardir in parts): raise error.Abort(_("path contains illegal component: %s") % path) # Windows shortname aliases for p in parts: if "~" in p: first, last = p.split("~", 1) if last.isdigit() and first.upper() in ["HG", "HG8B6C"]: raise error.Abort(_("path contains illegal component: %s") % path) if '.hg' in _lowerclean(path): lparts = [_lowerclean(p.lower()) for p in parts] for p in '.hg', '.hg.': if p in lparts[1:]: pos = lparts.index(p) base = os.path.join(*parts[:pos]) raise error.Abort(_("path '%s' is inside nested repo %r") % (path, base)) normparts = util.splitpath(normpath) assert len(parts) == len(normparts) parts.pop() normparts.pop() prefixes = [] # It's important that we check the path parts starting from the root. # This means we won't accidentaly traverse a symlink into some other # filesystem (which is potentially expensive to access). for i in range(len(parts)): prefix = os.sep.join(parts[:i + 1]) normprefix = os.sep.join(normparts[:i + 1]) if normprefix in self.auditeddir: continue if self._realfs: self._checkfs(prefix, path) prefixes.append(normprefix) self.audited.add(normpath) # only add prefixes to the cache after checking everything: we don't # want to add "foo/bar/baz" before checking if there's a "foo/.hg" self.auditeddir.update(prefixes) def _checkfs(self, prefix, path): """raise exception if a file system backed check fails""" curpath = os.path.join(self.root, prefix) try: st = os.lstat(curpath) except OSError as err: # EINVAL can be raised as invalid path syntax under win32. # They must be ignored for patterns can be checked too. if err.errno not in (errno.ENOENT, errno.ENOTDIR, errno.EINVAL): raise else: if stat.S_ISLNK(st.st_mode): msg = _('path %r traverses symbolic link %r') % (path, prefix) raise error.Abort(msg) elif (stat.S_ISDIR(st.st_mode) and os.path.isdir(os.path.join(curpath, '.hg'))): if not self.callback or not self.callback(curpath): msg = _("path '%s' is inside nested repo %r") raise error.Abort(msg % (path, prefix)) def check(self, path): try: self(path) return True except (OSError, error.Abort): return False def canonpath(root, cwd, myname, auditor=None): '''return the canonical path of myname, given cwd and root''' if util.endswithsep(root): rootsep = root else: rootsep = root + os.sep name = myname if not os.path.isabs(name): name = os.path.join(root, cwd, name) name = os.path.normpath(name) if auditor is None: auditor = pathauditor(root) if name != rootsep and name.startswith(rootsep): name = name[len(rootsep):] auditor(name) return util.pconvert(name) elif name == root: return '' else: # Determine whether `name' is in the hierarchy at or beneath `root', # by iterating name=dirname(name) until that causes no change (can't # check name == '/', because that doesn't work on windows). The list # `rel' holds the reversed list of components making up the relative # file name we want. rel = [] while True: try: s = util.samefile(name, root) except OSError: s = False if s: if not rel: # name was actually the same as root (maybe a symlink) return '' rel.reverse() name = os.path.join(*rel) auditor(name) return util.pconvert(name) dirname, basename = util.split(name) rel.append(basename) if dirname == name: break name = dirname # A common mistake is to use -R, but specify a file relative to the repo # instead of cwd. Detect that case, and provide a hint to the user. hint = None try: if cwd != root: canonpath(root, root, myname, auditor) hint = (_("consider using '--cwd %s'") % os.path.relpath(root, cwd)) except error.Abort: pass raise error.Abort(_("%s not under root '%s'") % (myname, root), hint=hint) def normasprefix(path): '''normalize the specified path as path prefix Returned value can be used safely for "p.startswith(prefix)", "p[len(prefix):]", and so on. For efficiency, this expects "path" argument to be already normalized by "os.path.normpath", "os.path.realpath", and so on. See also issue3033 for detail about need of this function. >>> normasprefix('/foo/bar').replace(os.sep, '/') '/foo/bar/' >>> normasprefix('/').replace(os.sep, '/') '/' ''' d, p = os.path.splitdrive(path) if len(p) != len(os.sep): return path + os.sep else: return path # forward two methods from posixpath that do what we need, but we'd # rather not let our internals know that we're thinking in posix terms # - instead we'll let them be oblivious. join = posixpath.join dirname = posixpath.dirname