checkheads: attend to phases when computing new heads with obsolete

Checkheads was more permissive than expected. When the remote heads
are public we don't need to search for successors. None will make a
public head disappear.

mercurial/discovery.py

@@ -293,11 +293,14 b' def checkheads(repo, remote, outgoing, r'
             # more tricky for unsynced changes.
             newhs = set()
             for nh in candidate_newhs:
-                for suc in obsolete.anysuccessors(repo.obsstore, nh):
-                    if suc != nh and suc in allmissing:
-                        break
+                if repo[nh].phase() <= phases.public:
+                    newhs.add(nh)
                 else:
-                    newhs.add(nh)
+                    for suc in obsolete.anysuccessors(repo.obsstore, nh):
+                        if suc != nh and suc in allmissing:
+                            break
+                    else:
+                        newhs.add(nh)
         else:
             newhs = candidate_newhs
         if len(newhs) > len(oldhs):

tests/test-obsolete-checkheads.t

@@ -71,13 +71,72 b' Push should not warn about creating new '
   adding file changes
   added 1 changesets with 1 changes to 1 files (+1 heads)
 
-old head is obsolete but replacement in not pushed
+old head is now public (public local version)
+=============================================
+
+setup
+
+  $ rm -fr ../remote
+  $ cp -r ../backup1 ../remote
+  $ hg -R ../remote phase --public c70b08862e08
+  $ hg pull -v
+  pulling from $TESTTMP/remote
+  searching for changes
+  no changes found
+  $ hg glog --hidden
+  @  71e3228bffe1 (draft) add new
+  |
+  | o  c70b08862e08 (public) add old
+  |/
+  o  b4952fcf48cf (public) add base
+  
+
+Abort: old will still be an head because it's public.
+
+  $ hg push
+  pushing to $TESTTMP/remote
+  searching for changes
+  abort: push creates new remote head 71e3228bffe1!
+  (did you forget to merge? use push -f to force)
+  [255]
+
+old head is now public (public remote version)
+==============================================
+
+TODO: Not implemented yet.
+
+# setup
+#
+#   $ rm -fr ../remote
+#   $ cp -r ../backup1 ../remote
+#   $ hg -R ../remote phase --public c70b08862e08
+#   $ hg phase --draft --force c70b08862e08
+#   $ hg glog --hidden
+#   @  71e3228bffe1 (draft) add new
+#   |
+#   | x  c70b08862e08 (draft) add old
+#   |/
+#   o  b4952fcf48cf (public) add base
+#
+#
+#
+# Abort: old will still be an head because it's public.
+#
+#   $ hg push
+#   pushing to $TESTTMP/remote
+#   searching for changes
+#   abort: push creates new remote head 71e3228bffe1!
+#   (did you forget to merge? use push -f to force)
+#   [255]
+
+old head is obsolete but replacement is not pushed
 ==================================================
 
 setup
 
   $ rm -fr ../remote
   $ cp -r ../backup1 ../remote
+  $ hg phase --draft --force '(0::) - 0'
   $ hg up -q '.^'
   $ mkcommit other
   created new head