merge: fix race that could cause wrong size in dirstate
The problem is that hg merge/update/etc work the following way:
1. figure out what files to update
2. apply the update to disk
3. apply the update to in-memory dirstate
4. write dirstate
where step3 looks at the filesystem and assumes it sees the result of
step2. If a file is changed between step2 and step3, step3 will record
incorrect information in the dirstate.
I avoid this by passing the size step3 needs directly from step2, for
the common path (not implemented for change/delete conflicts for
instance).
I didn't fix the same race for the exec bit for now, because it's less
likely to be problematic and I had trouble due to the fact that the
dirstate stores the permissions differently from the manifest (st_mode
vs '' 'l' 'x'), in combination with tests that pretend that symlinks
are not supported.
However, I moved the lstat from step3 to step2, which should tighten
the race window markedly, both for the exec bit and for the mtime.
Differential Revision: https://phab.mercurial-scm.org/D6475
# narrowdirstate.py - extensions to mercurial dirstate to support narrow clones
#
# Copyright 2017 Google, Inc.
#
# 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
from mercurial.i18n import _
from mercurial import (
error,
)
def wrapdirstate(repo, dirstate):
"""Add narrow spec dirstate ignore, block changes outside narrow spec."""
def _editfunc(fn):
def _wrapper(self, *args, **kwargs):
narrowmatch = repo.narrowmatch()
for f in args:
if f is not None and not narrowmatch(f) and f not in self:
raise error.Abort(_("cannot track '%s' - it is outside " +
"the narrow clone") % f)
return fn(self, *args, **kwargs)
return _wrapper
class narrowdirstate(dirstate.__class__):
# Prevent adding/editing/copying/deleting files that are outside the
# sparse checkout
@_editfunc
def normal(self, *args, **kwargs):
return super(narrowdirstate, self).normal(*args, **kwargs)
@_editfunc
def add(self, *args):
return super(narrowdirstate, self).add(*args)
@_editfunc
def normallookup(self, *args):
return super(narrowdirstate, self).normallookup(*args)
@_editfunc
def copy(self, *args):
return super(narrowdirstate, self).copy(*args)
@_editfunc
def remove(self, *args):
return super(narrowdirstate, self).remove(*args)
@_editfunc
def merge(self, *args):
return super(narrowdirstate, self).merge(*args)
def rebuild(self, parent, allfiles, changedfiles=None):
if changedfiles is None:
# Rebuilding entire dirstate, let's filter allfiles to match the
# narrowspec.
allfiles = [f for f in allfiles if repo.narrowmatch()(f)]
super(narrowdirstate, self).rebuild(parent, allfiles, changedfiles)
dirstate.__class__ = narrowdirstate
return dirstate