histedit: omit useless message from update (edit)

specifically:
0 files updated, 0 files merged, 0 files removed, 0 files unresolved

hgext/histedit.py

@@ -602,7 +602,7 b' class edit(histeditaction):'
     def run(self):
         repo = self.repo
         rulectx = repo[self.node]
-        hg.update(repo, self.state.parentctxnode)
+        hg.update(repo, self.state.parentctxnode, quietempty=True)
         applychanges(repo.ui, repo, rulectx, {})
         raise error.InterventionRequired(
             _('Make changes as needed, you may commit or record as needed '

tests/test-histedit-no-change.t

@@ -146,7 +146,6 b' check state of working copy'
   When you are finished, run hg histedit --continue to resume.
   $ continueediting true "(leaving commit message unaltered)"
   % finalize changeset editing (leaving commit message unaltered)
-  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
   Make changes as needed, you may commit or record as needed now.
   When you are finished, run hg histedit --continue to resume.
   $ graphlog "log after first edit"
@@ -212,7 +211,6 b' aborting and not changing files can skip'
   $ startediting 1 1 "(not changing anything)" # edit the 3rd of 3 changesets
   % start editing the history (not changing anything)
   | edit 292aec348d9e 6 closebranch
-  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
   Make changes as needed, you may commit or record as needed now.
   When you are finished, run hg histedit --continue to resume.
   $ hg histedit --abort