merge: make applyupdates() not mutate mresult argument
We have an extension at work that overrides `merge.applyupdates()` to
make it skip some writes and instead instruct the virtual filesystem
we use to get a different version. That override doesn't work
correctly when doing `hg co -m` and there's a modified file in the
dirstate that's deleted in the destination. That's because
`applyupdates()` mutates its `mresult` argument and our extension had
passed in a modified copied of `mresult` to the overridden function,
which resulted in the mutation not having any effect. This patch fixes
that by letting the caller (i.e. `merge._update()`) update `mresult`
with the extra actions instead. Besides fixing our internal extension,
that seems cleaner to me anyway (better to not mutate `mresult` only
in some cases and we can skip some of the logic if we're not going to
update the dirstate anyway).
Differential Revision: https://phab.mercurial-scm.org/D10830
# dirstateguard.py - class to allow restoring dirstate after failure
#
# Copyright 2005-2007 Olivia Mackall <olivia@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.
from __future__ import absolute_import
import os
from .i18n import _
from . import (
error,
narrowspec,
requirements,
util,
)
class dirstateguard(util.transactional):
"""Restore dirstate at unexpected failure.
At the construction, this class does:
- write current ``repo.dirstate`` out, and
- save ``.hg/dirstate`` into the backup file
This restores ``.hg/dirstate`` from backup file, if ``release()``
is invoked before ``close()``.
This just removes the backup file at ``close()`` before ``release()``.
"""
def __init__(self, repo, name):
self._repo = repo
self._active = False
self._closed = False
def getname(prefix):
fd, fname = repo.vfs.mkstemp(prefix=prefix)
os.close(fd)
return fname
self._backupname = getname(b'dirstate.backup.%s.' % name)
repo.dirstate.savebackup(repo.currenttransaction(), self._backupname)
# Don't make this the empty string, things may join it with stuff and
# blindly try to unlink it, which could be bad.
self._narrowspecbackupname = None
if requirements.NARROW_REQUIREMENT in repo.requirements:
self._narrowspecbackupname = getname(
b'narrowspec.backup.%s.' % name
)
narrowspec.savewcbackup(repo, self._narrowspecbackupname)
self._active = True
def __del__(self):
if self._active: # still active
# this may occur, even if this class is used correctly:
# for example, releasing other resources like transaction
# may raise exception before ``dirstateguard.release`` in
# ``release(tr, ....)``.
self._abort()
def close(self):
if not self._active: # already inactivated
msg = (
_(b"can't close already inactivated backup: %s")
% self._backupname
)
raise error.Abort(msg)
self._repo.dirstate.clearbackup(
self._repo.currenttransaction(), self._backupname
)
if self._narrowspecbackupname:
narrowspec.clearwcbackup(self._repo, self._narrowspecbackupname)
self._active = False
self._closed = True
def _abort(self):
if self._narrowspecbackupname:
narrowspec.restorewcbackup(self._repo, self._narrowspecbackupname)
self._repo.dirstate.restorebackup(
self._repo.currenttransaction(), self._backupname
)
self._active = False
def release(self):
if not self._closed:
if not self._active: # already inactivated
msg = (
_(b"can't release already inactivated backup: %s")
% self._backupname
)
raise error.Abort(msg)
self._abort()