--- a/hgext3rd/evolve/rewriteutil.py	Mon Jul 24 01:04:40 2017 +0200
+++ b/hgext3rd/evolve/rewriteutil.py	Mon Jul 24 02:06:14 2017 +0200
@@ -37,7 +37,9 @@
     <action> can be used to control the commit message.
     """
     if repo.revs('%ld and public()', revs):
-        raise error.Abort(_("cannot %s public changesets") % action)
+        msg = _("cannot %s public changesets") % action
+        hint = _("see 'hg help phases' for details")
+        raise error.Abort(msg, hint=hint)
 
 def bookmarksupdater(repo, oldid, tr):
     """Return a callable update(newid) updating the current bookmark

--- a/tests/test-fold.t	Mon Jul 24 01:04:40 2017 +0200
+++ b/tests/test-fold.t	Mon Jul 24 02:06:14 2017 +0200
@@ -74,6 +74,7 @@
   $ hg phase --public 0
   $ hg fold --from -r 0
   abort: cannot fold public changesets
+  (see 'hg help phases' for details)
   [255]
 
 Test actual folding

--- a/tests/test-metaedit.t	Mon Jul 24 01:04:40 2017 +0200
+++ b/tests/test-metaedit.t	Mon Jul 24 02:06:14 2017 +0200
@@ -104,6 +104,7 @@
   [255]
   $ hg metaedit -r 0 --fold
   abort: cannot fold public changesets
+  (see 'hg help phases' for details)
   [255]
   $ hg metaedit 'desc(C) + desc(F)' --fold
   abort: cannot fold non-linear revisions (multiple roots given)