fold: clarify message for empty revision set and abort instead (BC) I find it clearer that there are no revisions to fold because none were specified. Otherwise it seems ambiguous: maybe there are no revisions to fold because it's impossible to fold whatever was given? In analogy of other commands that are given no revisions (e.g. strip, graft), this is also now an abort instead of a mere error message, which is a BC.

--- a/hgext/evolve.py	Fri Jul 04 09:29:13 2014 -0400
+++ b/hgext/evolve.py	Mon Jun 30 10:27:15 2014 -0400
@@ -2098,8 +2098,7 @@
     else:
         revs = ()
     if not revs:
-        ui.write_err('no revision to fold\n')
-        return 1
+        raise util.Abort(_('no revisions specified'))
     roots = repo.revs('roots(%ld)', revs)
     if len(roots) > 1:
         raise util.Abort("set has multiple roots")