graft: remark on empty graft

mercurial/commands.py

@@ -2719,8 +2719,10 b' def graft(ui, repo, *revs, **opts):'
             date = ctx.date()
             if opts.get('date'):
                 date = opts['date']
-            repo.commit(text=ctx.description(), user=user,
+            node = repo.commit(text=ctx.description(), user=user,
                         date=date, extra=extra, editor=editor)
+            if node is None:
+                ui.status(_('graft for revision %s is empty\n') % ctx.rev())
     finally:
         wlock.release()
 

tests/test-graft.t

@@ -132,6 +132,7 b' Graft out of order, skipping a merge and'
    b: local copied/moved to a -> m
   preserving b for resolve of b
   updating: b 1/1 files (100.00%)
+  graft for revision 1 is empty
   grafting revision 5
     searching for copies back to rev 1
   resolving manifests