rebase: add returning value from pullrebase function

So far pullrebase function has always returned None value, no matter
what orig function returned. This behaviour made impossible for
pull to change returned value from mercurial process (it has always
ended with 0 value by default). This patch makes pullrebase returning
with returned value from orig.

hgext/rebase.py

@@ -1096,6 +1096,7 b' def clearrebased(ui, repo, state, skippe'
 
 def pullrebase(orig, ui, repo, *args, **opts):
     'Call rebase after pull if the latter has been invoked with --rebase'
+    ret = None
     if opts.get('rebase'):
         wlock = lock = None
         try:
@@ -1113,7 +1114,7 b' def pullrebase(orig, ui, repo, *args, **'
                 pass
             commands.postincoming = _dummy
             try:
-                orig(ui, repo, *args, **opts)
+                ret = orig(ui, repo, *args, **opts)
             finally:
                 commands.postincoming = origpostincoming
             revspostpull = len(repo)
@@ -1140,7 +1141,9 b' def pullrebase(orig, ui, repo, *args, **'
     else:
         if opts.get('tool'):
             raise error.Abort(_('--tool can only be used with --rebase'))
-        orig(ui, repo, *args, **opts)
+        ret = orig(ui, repo, *args, **opts)
+
+    return ret
 
 def _setrebasesetvisibility(repo, revs):
     """store the currently rebased set on the repo object