mq: factor out push conditions checks

Some extensions (e.g. hgsubversion) completely override push command. Because
extensions load order is unspecified, if hgsubversion loads before mq, mq
checks about not pushing applied patches will be bypassed. Short of finding a
way to fix load order, extracting the checking logic will allow
hgsubversion-like extensions to run the check themselves.

hgext/mq.py

@@ -2919,7 +2919,7 b' def reposetup(ui, repo):'
             return super(mqrepo, self).commit(text, user, date, match, force,
                                               editor, extra)
 
-        def push(self, remote, force=False, revs=None, newbranch=False):
+        def checkpush(self, force, revs):
             if self.mq.applied and not force:
                 haspatches = True
                 if revs:
@@ -2930,7 +2930,7 b' def reposetup(ui, repo):'
                     haspatches = bool([n for n in revs if n in applied])
                 if haspatches:
                     raise util.Abort(_('source has mq patches applied'))
-            return super(mqrepo, self).push(remote, force, revs, newbranch)
+            super(mqrepo, self).checkpush(force, revs)
 
         def _findtags(self):
             '''augment tags from base class with patch tags'''

mercurial/localrepo.py

@@ -1305,6 +1305,13 b' class localrepository(repo.repository):'
         finally:
             lock.release()
 
+    def checkpush(self, force, revs):
+        """Extensions can override this function if additional checks have
+        to be performed before pushing, or call it if they override push
+        command.
+        """
+        pass
+
     def push(self, remote, force=False, revs=None, newbranch=False):
         '''Push outgoing changesets (limited by revs) from the current
         repository to remote. Return an integer:
@@ -1321,6 +1328,7 b' class localrepository(repo.repository):'
         # unbundle assumes local user cannot lock remote repo (new ssh
         # servers, http servers).
 
+        self.checkpush(force, revs)
         lock = None
         unbundle = remote.capable('unbundle')
         if not unbundle: