dirstate-guard: remove the feature

dirstate-guard: remove the feature

The dirstate guard duplicated some of the logic already implemented in the
transaction (and now the changing_* context).

However the feature was incomplete, for example, living only in memory meant we
could not recover from the hardest crash. In addition this duplicated with the
transaction logic meant things could go out of sync or step on each other.

Removing the feature now that we no longer needs it seems the safest.

--- a/mercurial/dirstateguard.py	Thu Feb 16 00:14:21 2023 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,96 +0,0 @@
-# dirstateguard.py - class to allow restoring dirstate after failure
-#
-# Copyright 2005-2007 Olivia 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.
-
-
-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()