view mercurial/dirstateguard.py @ 39996:dbcb466d0065

localrepo: define storage backend in creation options (API)

We add an experimental config option to define the storage backend
for new repositories. By default, it uses "revlogv1," which maps to
the current and only modern supported repository format.

We add a "backend" creation option to control which backend to
use. It defaults to using the value from the config option.

newreporequirements() will now barf if it sees a "backend" value
that isn't "revlogv1." This forces extensions to monkeypatch the
function to handle requirements derivation for custom backends.

In order for this to "just work," we factored out obtaining the
default creation options into its own function and made callers
of newreporequirements() responsible for passing in valid data.
Without this, direct callers of newreporequirements() wouldn't
get the proper results.

Differential Revision: https://phab.mercurial-scm.org/D4791

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

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

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