rollback: only restore dirstate and branch when appropriate.

If the working dir parent was destroyed by rollback, then the old
behaviour is perfectly reasonable: restore dirstate, branch, and
bookmarks. That way the working dir moves back to an existing
changeset rather than becoming an orphan.

But if the working dir parent was unaffected -- say, you updated to an
older changeset and then did rollback -- then it's silly to restore
dirstate and branch. So don't do that. Leave the status of the working
dir alone. (But always restore bookmarks, because that file refers to
changeset IDs that may have been destroyed.)

mercurial/localrepo.py

@@ -789,28 +789,35 b' class localrepository(repo.repository):'
         ui.status(msg)
         if dryrun:
             return 0
+
+        parents = self.dirstate.parents()
         transaction.rollback(self.sopener, self.sjoin('undo'), ui.warn)
-        util.rename(self.join('undo.dirstate'), self.join('dirstate'))
         if os.path.exists(self.join('undo.bookmarks')):
             util.rename(self.join('undo.bookmarks'),
                         self.join('bookmarks'))
-        try:
-            branch = self.opener.read('undo.branch')
-            self.dirstate.setbranch(branch)
-        except IOError:
-            ui.warn(_('named branch could not be reset: '
-                      'current branch is still \'%s\'\n')
-                    % self.dirstate.branch())
         self.invalidate()
-        self.dirstate.invalidate()
-        self.destroyed()
-        parents = tuple([p.rev() for p in self.parents()])
-        if len(parents) > 1:
-            ui.status(_('working directory now based on '
-                        'revisions %d and %d\n') % parents)
-        else:
-            ui.status(_('working directory now based on '
-                        'revision %d\n') % parents)
+
+        parentgone = (parents[0] not in self.changelog.nodemap or
+                      parents[1] not in self.changelog.nodemap)
+        if parentgone:
+            util.rename(self.join('undo.dirstate'), self.join('dirstate'))
+            try:
+                branch = self.opener.read('undo.branch')
+                self.dirstate.setbranch(branch)
+            except IOError:
+                ui.warn(_('named branch could not be reset: '
+                          'current branch is still \'%s\'\n')
+                        % self.dirstate.branch())
+
+            self.dirstate.invalidate()
+            self.destroyed()
+            parents = tuple([p.rev() for p in self.parents()])
+            if len(parents) > 1:
+                ui.status(_('working directory now based on '
+                            'revisions %d and %d\n') % parents)
+            else:
+                ui.status(_('working directory now based on '
+                            'revision %d\n') % parents)
         return 0
 
     def invalidatecaches(self):

tests/test-acl.t

@@ -121,7 +121,6 b' Extension disabled for lack of a hook'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 0 (undo push)
-  working directory now based on revision 0
   0:6675d58eff77
   
 
@@ -179,7 +178,6 b' Extension disabled for lack of acl.sourc'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 0 (undo push)
-  working directory now based on revision 0
   0:6675d58eff77
   
 
@@ -247,7 +245,6 b' No [acl.allow]/[acl.deny]'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 0 (undo push)
-  working directory now based on revision 0
   0:6675d58eff77
   
 
@@ -729,7 +726,6 b' barney is allowed everywhere'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 0 (undo push)
-  working directory now based on revision 0
   0:6675d58eff77
   
 
@@ -1038,7 +1034,6 b' acl.config can set only [acl.allow]/[acl'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 0 (undo push)
-  working directory now based on revision 0
   0:6675d58eff77
   
 
@@ -1114,7 +1109,6 b' fred is always allowed'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 0 (undo push)
-  working directory now based on revision 0
   0:6675d58eff77
   
 
@@ -1261,7 +1255,6 b' OS-level groups'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 0 (undo push)
-  working directory now based on revision 0
   0:6675d58eff77
   
 
@@ -1456,7 +1449,6 b' No branch acls specified'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 2 (undo push)
-  working directory now based on revision 2
   2:fb35475503ef
   
 
@@ -1753,7 +1745,6 b' Branch acl allow other'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 2 (undo push)
-  working directory now based on revision 2
   2:fb35475503ef
   
 
@@ -1838,7 +1829,6 b' push foobar into the remote'
   updating the branch cache
   checking for updated bookmarks
   repository tip rolled back to revision 2 (undo push)
-  working directory now based on revision 2
   2:fb35475503ef
   
 Branch acl conflicting deny

tests/test-bundle-r.t

@@ -154,7 +154,6 b''
   4 files, 9 changesets, 7 total revisions
   $ hg rollback
   repository tip rolled back to revision 4 (undo pull)
-  working directory now based on revision -1
   $ cd ..
 
 should fail
@@ -232,7 +231,6 b' revision 8'
   4 files, 9 changesets, 7 total revisions
   $ hg rollback
   repository tip rolled back to revision 2 (undo unbundle)
-  working directory now based on revision 2
 
 revision 2
 
@@ -257,7 +255,6 b' revision 4'
   2 files, 5 changesets, 5 total revisions
   $ hg rollback
   repository tip rolled back to revision 2 (undo unbundle)
-  working directory now based on revision 2
   $ hg unbundle ../test-bundle-branch2.hg
   adding changesets
   adding manifests
@@ -277,7 +274,6 b' revision 6'
   3 files, 7 changesets, 6 total revisions
   $ hg rollback
   repository tip rolled back to revision 2 (undo unbundle)
-  working directory now based on revision 2
   $ hg unbundle ../test-bundle-cset-7.hg
   adding changesets
   adding manifests

tests/test-bundle.t

@@ -90,7 +90,6 b' Rollback empty'
 
   $ hg -R empty rollback
   repository tip rolled back to revision -1 (undo pull)
-  working directory now based on revision -1
 
 Pull full.hg into empty again (using --cwd)
 
@@ -121,7 +120,6 b' Rollback empty'
 
   $ hg -R empty rollback
   repository tip rolled back to revision -1 (undo pull)
-  working directory now based on revision -1
 
 Pull full.hg into empty again (using -R)
 
@@ -219,7 +217,6 b' Rollback empty'
 
   $ hg rollback
   repository tip rolled back to revision -1 (undo pull)
-  working directory now based on revision -1
   $ cd ..
 
 Log -R bundle:empty+full.hg

tests/test-convert-cvs.t

@@ -112,7 +112,6 b' convert fresh repo with --filemap'
   1 import
   filtering out empty revision
   repository tip rolled back to revision 0 (undo commit)
-  working directory now based on revision -1
   0 ci0
   updating tags
   $ hgcat b/c

tests/test-eol-hook.t

@@ -161,7 +161,6 b' We can fix the head and push again'
   added 3 changesets with 3 changes to 2 files (+1 heads)
   $ hg -R ../main rollback
   repository tip rolled back to revision 5 (undo push)
-  working directory now based on revision -1
 
 Test it still fails with checkallhook
 

tests/test-hook.t

@@ -277,7 +277,6 b' outgoing hooks can see env vars'
   (run 'hg update' to get a working copy)
   $ hg rollback
   repository tip rolled back to revision 3 (undo pull)
-  working directory now based on revision 0
 
 preoutgoing hook can prevent outgoing changes
 

tests/test-import-bypass.t

@@ -62,7 +62,6 b' Test --user, --date and --message'
   
   $ hg rollback
   repository tip rolled back to revision 1 (undo commit)
-  working directory now based on revision 0
 
 Test --import-branch
 
@@ -75,7 +74,6 b' Test --import-branch'
   
   $ hg rollback
   repository tip rolled back to revision 1 (undo commit)
-  working directory now based on revision 0
 
 Test --strip
 
@@ -98,7 +96,6 b' Test --strip'
   applying patch from stdin
   $ hg rollback
   repository tip rolled back to revision 1 (undo commit)
-  working directory now based on revision 0
 
 Test unsupported combinations
 

tests/test-notify-changegroup.t

@@ -74,7 +74,6 b' push'
   +a
   $ hg --cwd a rollback
   repository tip rolled back to revision -1 (undo push)
-  working directory now based on revision -1
 
 unbundle with unrelated source
 
@@ -89,7 +88,6 b' unbundle with unrelated source'
   (run 'hg update' to get a working copy)
   $ hg --cwd a rollback
   repository tip rolled back to revision -1 (undo unbundle)
-  working directory now based on revision -1
 
 unbundle with correct source
 

tests/test-notify.t

@@ -200,7 +200,6 b' fail for config file is missing'
 
   $ hg --cwd b rollback
   repository tip rolled back to revision 0 (undo pull)
-  working directory now based on revision 0
   $ hg --cwd b pull ../a 2>&1 | grep 'error.*\.notify\.conf' > /dev/null && echo pull failed
   pull failed
   $ touch ".notify.conf"
@@ -209,7 +208,6 b' pull'
 
   $ hg --cwd b rollback
   repository tip rolled back to revision 0 (undo pull)
-  working directory now based on revision 0
   $ hg --traceback --cwd b pull ../a  | \
   >   python -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
   pulling from ../a
@@ -254,7 +252,6 b' pull'
 
   $ hg --cwd b rollback
   repository tip rolled back to revision 0 (undo pull)
-  working directory now based on revision 0
   $ hg --traceback --cwd b pull ../a | \
   >   python -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
   pulling from ../a

tests/test-push-http.t

@@ -64,7 +64,6 b' expect success'
   % serve errors
   $ hg rollback
   repository tip rolled back to revision 0 (undo serve)
-  working directory now based on revision 0
 
 expect success, server lacks the httpheader capability
 
@@ -81,7 +80,6 b' expect success, server lacks the httphea'
   % serve errors
   $ hg rollback
   repository tip rolled back to revision 0 (undo serve)
-  working directory now based on revision 0
 
 expect success, server lacks the unbundlehash capability
 
@@ -98,7 +96,6 b' expect success, server lacks the unbundl'
   % serve errors
   $ hg rollback
   repository tip rolled back to revision 0 (undo serve)
-  working directory now based on revision 0
 
 expect authorization error: all users denied
 

tests/test-rollback.t

@@ -64,6 +64,35 b' Test rollback of hg before issue 902 was'
   $ hg branch
   test
 
+working dir unaffected by rollback: do not restore dirstate et. al.
+  $ hg log --template '{rev}  {branch}  {desc|firstline}\n'
+  0  default  add a again
+  $ hg status
+  M a
+  $ hg bookmark foo
+  $ hg commit -m'modify a again'
+  $ echo b > b
+  $ hg commit -Am'add b'
+  adding b
+  $ hg log --template '{rev}  {branch}  {desc|firstline}\n'
+  2  test  add b
+  1  test  modify a again
+  0  default  add a again
+  $ hg update default
+  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  $ hg bookmark bar
+  $ cat .hg/undo.branch ; echo
+  test
+  $ hg rollback
+  repository tip rolled back to revision 1 (undo commit)
+  $ hg id -n
+  0
+  $ hg branch
+  default
+  $ cat .hg/bookmarks.current ; echo
+  bar
+  $ hg bookmark --delete foo
+
 rollback by pretxncommit saves commit message (issue 1635)
 
   $ echo a >> a
@@ -102,18 +131,18 b' test rollback on served repository'
   adding changesets
   adding manifests
   adding file changes
-  added 2 changesets with 2 changes to 1 files
+  added 3 changesets with 2 changes to 1 files (+1 heads)
   updating to branch default
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd u
   $ hg id default
-  8902593132ae
+  068774709090
 
 now rollback and observe that 'hg serve' reloads the repository and
 presents the correct tip changeset:
 
   $ hg -R ../t rollback
-  repository tip rolled back to revision 0 (undo commit)
+  repository tip rolled back to revision 1 (undo commit)
   working directory now based on revision 0
   $ hg id default
-  23b0221f3370
+  791dd2169706

tests/test-url-rev.t

@@ -102,7 +102,6 b' Changing original repo:'
   $ cd clone
   $ hg rollback
   repository tip rolled back to revision 1 (undo push)
-  working directory now based on revision 1
 
   $ hg -q incoming
   2:faba9097cad4
@@ -147,10 +146,6 b' No new revs, no update:'
 
   $ hg rollback
   repository tip rolled back to revision 1 (undo pull)
-  working directory now based on revision 1
-
-  $ hg up -C 0
-  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
   $ hg parents -q
   0:1f0dee641bb7