narrow: make dirstateguard back up and restore working copy narrowspec instead

narrow: make dirstateguard back up and restore working copy narrowspec instead

We used to have only one narrowspec for the store and the working
copy, but now that we have one narrowspec for each, it seems clear
that the dirstateguard was supposed to back up and restore the
narrowspec associated with the working copy, not the one associated
with the store.

clearbackup() (for the store narrowspec) is not needed because the
presence of the file in localrepository._journalfiles() takes care of
that.

Differential Revision: https://phab.mercurial-scm.org/D5504

--- a/mercurial/dirstateguard.py	Thu Jan 10 13:36:25 2019 -0800
+++ b/mercurial/dirstateguard.py	Sat Dec 29 22:27:39 2018 -0800
@@ -37,7 +37,7 @@
         self._narrowspecbackupname = ('narrowspec.backup.%s.%d' %
                                       (name, id(self)))
         repo.dirstate.savebackup(repo.currenttransaction(), self._backupname)
-        narrowspec.savebackup(repo, self._narrowspecbackupname)
+        narrowspec.savewcbackup(repo, self._narrowspecbackupname)
         self._active = True
 
     def __del__(self):
@@ -56,12 +56,12 @@
 
         self._repo.dirstate.clearbackup(self._repo.currenttransaction(),
                                          self._backupname)
-        narrowspec.clearbackup(self._repo, self._narrowspecbackupname)
+        narrowspec.clearwcbackup(self._repo, self._narrowspecbackupname)
         self._active = False
         self._closed = True
 
     def _abort(self):
-        narrowspec.restorebackup(self._repo, self._narrowspecbackupname)
+        narrowspec.restorewcbackup(self._repo, self._narrowspecbackupname)
         self._repo.dirstate.restorebackup(self._repo.currenttransaction(),
                                            self._backupname)
         self._active = False

--- a/mercurial/narrowspec.py	Thu Jan 10 13:36:25 2019 -0800
+++ b/mercurial/narrowspec.py	Sat Dec 29 22:27:39 2018 -0800
@@ -185,10 +185,25 @@
         return
     util.rename(repo.svfs.join(backupname), repo.svfs.join(FILENAME))
 
-def clearbackup(repo, backupname):
+def savewcbackup(repo, backupname):
     if repository.NARROW_REQUIREMENT not in repo.requirements:
         return
-    repo.svfs.unlink(backupname)
+    vfs = repo.vfs
+    vfs.tryunlink(backupname)
+    # It may not exist in old repos
+    if vfs.exists(DIRSTATE_FILENAME):
+        util.copyfile(vfs.join(DIRSTATE_FILENAME), vfs.join(backupname),
+                      hardlink=True)
+
+def restorewcbackup(repo, backupname):
+    if repository.NARROW_REQUIREMENT not in repo.requirements:
+        return
+    util.rename(repo.vfs.join(backupname), repo.vfs.join(DIRSTATE_FILENAME))
+
+def clearwcbackup(repo, backupname):
+    if repository.NARROW_REQUIREMENT not in repo.requirements:
+        return
+    repo.vfs.unlink(backupname)
 
 def restrictpatterns(req_includes, req_excludes, repo_includes, repo_excludes):
     r""" Restricts the patterns according to repo settings,