rebase: perform update through the 'update' command

The update logic have grow more and more complicated over time (eg bookmark
movement, new destination logic, warning on other head, etc). The rebase
extension was reimplementing its own basic version of update to be used by 'hg
pull --rebase'. We remove the custom code and use a combination of higher level
functions.

A test is added to check that the update is properly warning about other branch
heads.

hgext/rebase.py

@@ -16,7 +16,7 b' https://mercurial-scm.org/wiki/RebaseExt'
 
 from mercurial import hg, util, repair, merge, cmdutil, commands, bookmarks
 from mercurial import extensions, patch, scmutil, phases, obsolete, error
-from mercurial import copies, repoview, revset
+from mercurial import copies, destutil, repoview, revset
 from mercurial.commands import templateopts
 from mercurial.node import nullrev, nullid, hex, short
 from mercurial.lock import release
@@ -1145,7 +1145,6 b' def pullrebase(orig, ui, repo, *args, **'
                 ui.debug('--update and --rebase are not compatible, ignoring '
                          'the update flag\n')
 
-            movemarkfrom = repo['.'].node()
             revsprepull = len(repo)
             origpostincoming = commands.postincoming
             def _dummy(*args, **kwargs):
@@ -1166,15 +1165,11 b' def pullrebase(orig, ui, repo, *args, **'
                 if 'source' in opts:
                     del opts['source']
                 if rebase(ui, repo, **opts) == _nothingtorebase():
-                    branch = repo[None].branch()
-                    dest = repo[branch].rev()
-                    if dest != repo['.'].rev():
-                        # there was nothing to rebase we force an update
-                        hg.update(repo, dest)
-                        if bookmarks.update(repo, [movemarkfrom],
-                                            repo['.'].node()):
-                            ui.status(_("updating bookmark %s\n")
-                                      % repo._activebookmark)
+                    rev, _a, _b = destutil.destupdate(repo)
+                    if rev != repo['.'].rev(): # we could update
+                        # not passing argument to get the bare update behavior
+                        # with warning and trumpets
+                        commands.update(ui, repo)
         finally:
             release(lock, wlock)
     else:

tests/test-rebase-pull.t

@@ -266,3 +266,46 b' pull --rebase only update if there is no'
   |
   o  0: 'C1'
   
+
+pull --rebase update (no rebase) use proper update:
+
+- warn about other head.
+
+  $ cd ../a
+  $ echo R6 > R6
+  $ hg ci -Am R6
+  adding R6
+  $ cd ../c
+  $ hg up 'desc(R5)'
+  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  $ hg pull --rebase
+  pulling from $TESTTMP/a (glob)
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files (+1 heads)
+  nothing to rebase - working directory parent is already an ancestor of destination 65bc164c1d9b
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
+  $ hg tglog
+  @  9: 'R6'
+  |
+  | o  8: 'L2'
+  | |
+  | o  7: 'L1'
+  |/
+  o  6: 'R5'
+  |
+  o  5: 'R4'
+  |
+  o  4: 'R3'
+  |
+  o  3: 'R2'
+  |
+  o  2: 'R1'
+  |
+  o  1: 'C2'
+  |
+  o  0: 'C1'
+