discovery: replace "heads" by "changesets" in a output note (BC) When using `hg push --rev X`, the subset considered by discovery is only `::X`. In addition, `X` can be any local revisions not just local heads. As a result the message "all local heads known locally" can be misleading. We replace it with the more accurate "all local changesets known remotely". The message appears when in verbose not, so this is stricly speaking a BC breakage. I am not sure this would be a real issue in practice...

--- a/mercurial/setdiscovery.py	Thu Sep 05 16:32:33 2019 -0700
+++ b/mercurial/setdiscovery.py	Sat Apr 27 02:04:05 2019 +0200
@@ -389,7 +389,7 @@
         return srvheadhashes, False, srvheadhashes
 
     if len(sample) == len(ownheads) and all(yesno):
-        ui.note(_("all local heads known remotely\n"))
+        ui.note(_("all local changesets known remotely\n"))
         ownheadhashes = [clnode(r) for r in ownheads]
         return ownheadhashes, True, srvheadhashes