--- a/hgext/evolve.py	Wed Nov 30 11:17:55 2016 +0000
+++ b/hgext/evolve.py	Wed Nov 23 21:00:42 2016 +0530
@@ -2514,7 +2514,8 @@
             raise error.Abort('nothing to prune')
 
         if _disallowednewunstable(repo, revs):
-            raise error.Abort(_("cannot prune in the middle of a stack"))
+            raise error.Abort(_("cannot prune in the middle of a stack"),
+                        hint = _("new unstable changesets are not allowed"))
 
         # defines successors changesets
         sucs = scmutil.revrange(repo, succs)
@@ -3234,8 +3235,9 @@
             newunstable = _disallowednewunstable(repo, revs)
             if newunstable:
                 raise error.Abort(
-                    _('cannot edit commit information in the middle of a stack'),
-                    hint=_('%s will be affected') % repo[newunstable.first()])
+                    _('cannot edit commit information in the middle of a '\
+                    'stack'), hint=_('%s will become unstable and new unstable'\
+                    ' changes are not allowed') % repo[newunstable.first()])
             root = head = repo[revs.first()]
 
         wctx = repo[None]
@@ -3299,7 +3301,8 @@
     head = repo[heads.first()]
     if _disallowednewunstable(repo, revs):
         raise error.Abort(_("cannot fold chain not ending with a head "\
-                            "or with branching"))
+                            "or with branching"), hint = _("new unstable"\
+                            " changesets are not allowed"))
     return root, head
 
 def _disallowednewunstable(repo, revs):