--- a/hgext/histedit.py	Thu Apr 18 15:13:35 2013 +0200
+++ b/hgext/histedit.py	Thu Apr 18 15:22:24 2013 +0200
@@ -717,6 +717,7 @@
     """
     parsed = []
     expected = set(str(c) for c in ctxs)
+    seen = set()
     if len(rules) != len(expected):
         raise util.Abort(_('must specify a rule for each changeset once'))
     for r in rules:
@@ -731,6 +732,9 @@
         if ha not in expected:
             raise util.Abort(
                 _('may not use changesets other than the ones listed'))
+        if ha in seen:
+            raise util.Abort(_('duplicated command for changeset %s') % ha)
+        seen.add(ha)
         if action not in actiontable:
             raise util.Abort(_('unknown action "%s"') % action)
         parsed.append([action, ha])

--- a/tests/test-histedit-arguments.t	Thu Apr 18 15:13:35 2013 +0200
+++ b/tests/test-histedit-arguments.t	Thu Apr 18 15:22:24 2013 +0200
@@ -124,6 +124,19 @@
   abort: unknown action "coin"
   [255]
 
+Test duplicated changeset
+---------------------------------------
+
+So one is missing and one appear twice.
+
+  $ HGEDITOR=cat hg histedit "tip^^" --commands - << EOF
+  > pick eb57da33312f 2 three
+  > pick eb57da33312f 2 three
+  > pick 08d98a8350f3 4 five
+  > EOF
+  abort: duplicated command for changeset eb57da33312f
+  [255]
+
 Test short version of command
 ---------------------------------------