view mercurial/dirstateguard.py @ 35237:8df8ce2cc5dd

remotenames: add functionality to store remotenames under .hg/hgremotenames/

This patch moves the functionality from remotenames extension to store
remotenames to core.

Storage format used by remotenames extension:

A single file `.hg/remotenames` with an entry in each line where each line is of
format:
`node nametype remotepath/name`
where nametype is either 'bookmarks' or 'branches'.

This was not the best way to store data, so while moving to core the storage
format was changed but yet not the final format. The storage format used by core
after this patch will be:

* A file for each type of name i.e. bookmarks and branches in .hg/remotenames/
  directory
* A version number on the top of the file. The version for current format is 0.
* An entry in each line where each line is of the format
`node\0remotepath\0name`

The logic to sync with existing remotenames file and saving journals and other
related things will be moved to core in next patches incrementally.

Thanks to Ryan, Augie and Durham for suggestions on storage format.

Previously reviewed as D939.

Differential Revision: https://phab.mercurial-scm.org/D1548

# dirstateguard.py - class to allow restoring dirstate after failure
#
# Copyright 2005-2007 Matt Mackall <[e-mail]>
#
# 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 .i18n import _

from . import (
    error,
    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
        self._backupname = 'dirstate.backup.%s.%d' % (name, id(self))
        repo.dirstate.savebackup(repo.currenttransaction(), self._backupname)
        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 = (_("can't close already inactivated backup: %s")
                   % self._backupname)
            raise error.Abort(msg)

        self._repo.dirstate.clearbackup(self._repo.currenttransaction(),
                                         self._backupname)
        self._active = False
        self._closed = True

    def _abort(self):
        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 = (_("can't release already inactivated backup: %s")
                       % self._backupname)
                raise error.Abort(msg)
            self._abort()