discovery: improve "note: unsynced remote changes!" warning This note (which actually is a warning) frequently caused confusion. "unsynced" is not a well established user-facing concept in Mercurial and the message was not very specific or helpful. Instead, show a messages like: remote has heads on branch 'default' that are not known locally: 6c0482d977a3 and show it before aborting on "push creates new remote head". This will also give more of a hint in the case where the branch has been closed remotely and 'hg heads' thus not would show any new heads after pulling. A similar (but actually very different) message was addressed in 6b618aa08b6e.

--- a/tests/test-ssh.t	Fri Feb 07 17:26:28 2014 +0100
+++ b/tests/test-ssh.t	Thu Feb 06 02:19:38 2014 +0100
@@ -223,7 +223,7 @@
   $ hg push
   pushing to ssh://user@dummy/remote
   searching for changes
-  note: unsynced remote changes!
+  remote has heads on branch 'default' that are not known locally: 6c0482d977a3
   remote: adding changesets
   remote: adding manifests
   remote: adding file changes