[PATCH 2 of 4 V6 STABLE] revert: be more helpful on uncommitted merges

[Kevin Bullock]

# HG changeset patch
# User Kevin Bullock <kbullock at ringworld.org>
# Date 1308626671 18000
# Branch stable
# Node ID 59f92ee58bc1ff014d11d009ab8e39ae86fb5af7
# Parent  10a8c14a8fdca3d00fee266b3af949f2bd5d74e5
revert: be more helpful on uncommitted merges

 BEFORE:
   $ hg revert
   abort: no files or directories specified
   (use --all to discard all changes)

 AFTER:
   $ hg revert
   abort: no files or directories specified
   (use --all to discard all changes, or 'hg update -C .' to cancel uncommitted merge)

diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -4181,8 +4181,12 @@
     parent, p2 = repo.dirstate.parents()
 
     if not pats and not opts.get('all'):
-        raise util.Abort(_('no files or directories specified'),
-                         hint=_('use --all to discard all changes'))
+        msg = _('no files or directories specified')
+        hint = _('use --all to discard all changes')
+        if p2 != nullid:
+            hint = _('use --all to discard all changes, or '
+                     "'hg update -C .' to cancel uncommitted merge")
+        raise util.Abort(msg, hint=hint)
 
     ctx = scmutil.revsingle(repo, opts.get('rev'))
     node = ctx.node()
diff --git a/tests/test-confused-revert.t b/tests/test-confused-revert.t
--- a/tests/test-confused-revert.t
+++ b/tests/test-confused-revert.t
@@ -60,7 +60,7 @@
 
   $ hg revert
   abort: no files or directories specified
-  (use --all to discard all changes)
+  (use --all to discard all changes, or 'hg update -C .' to cancel uncommitted merge)
   [255]
 
 Revert should be ok now: