histedit: protect against duplicated entries

Before this change one would issue rules with duplicated entries. For
this to happen some other changeset had to be missing to maintain the
rules length.

hgext/histedit.py

@@ -717,6 +717,7 b' def verifyrules(rules, repo, ctxs):'
     """
     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 b' def verifyrules(rules, repo, ctxs):'
         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])

tests/test-histedit-arguments.t

@@ -124,6 +124,19 b' Test unknown command'
   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
 ---------------------------------------