commands: always order heads recent to oldest

mercurial/commands.py

@@ -1447,9 +1447,10 b' def heads(ui, repo, *branchrevs, **opts)'
     if not heads:
         return 1
 
+    heads = sorted((repo[h] for h in heads), key=lambda x: -x.rev())
     displayer = cmdutil.show_changeset(ui, repo, opts)
-    for n in heads:
-        displayer.show(repo[n])
+    for ctx in heads:
+        displayer.show(ctx)
     displayer.close()
 
 def help_(ui, name=None, with_version=False):

tests/test-bheads.out

@@ -147,8 +147,8 b' 7: Adding c branch'
 abort: unknown revision 'z'!
 -------
 =======
-0: Adding root node
-1: Adding a branch
 7: Adding c branch
 6: Merging b branch head 2 and b branch head 3
 3: Adding b branch head 1
+1: Adding a branch
+0: Adding root node