view mercurial/dirstateguard.py @ 35714:113281667205

githelp: vendor Facebook authored extension

This commit vendors the Facebook-authored "githelp" extension. This
extension provides a "githelp" command that can be used to try to
convert a `git` command to its Mercurial equivalent. This functionality
is useful for Git users learning Mercurial.

The extension was copied from the
repository at revision 32ceeccb832c433b36e9af8196814b8e5a526775. The
following modifications were made:

* The "testedwith" value has been changed to match core's conventions.
* Support for a custom footer has been removed, as it is Facebook
  specific. The feature is useful. But the implementation wasn't
  appropriate for core.
* A test referencing "tweakdefaults" has been removed.
* Imports changed to match Mercurial's style convention.
* Double newlines in test removed.
* Pager activation changed to ui.pager().
* Initial line of githelp.py changed to add description of file.

The removal of the custom footer code was the only significant
source change. The rest were mostly cosmetic.

There are still some Facebook-isms in the extension. I'll address
these as follow-ups.

.. feature:: githelp extension

   The "githelp" extension provides the ``hg githelp`` command. This
   command attempts to convert a ``git`` command to its Mercurial
   equivalent. The extension can be useful to Git users new to
   Mercurial.

Differential Revision: https://phab.mercurial-scm.org/D1722

# 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()