backout: avoid redundant message examination

Before this patch, "hg backout" examines "--message" and "--logfile"
options explicitly.

But this examination is redundant, because "commitfunc()" can receive
the result of same examination by "cmdutil.logmessage()" in
"cmdutil.commit()" through "message" argument.

This patch avoids redundant message examination by "message"
examination in "commitfunc()".

mercurial/commands.py

@@ -487,13 +487,12 b' def backout(ui, repo, node=None, rev=Non'
             cmdutil.revert(ui, repo, rctx, repo.dirstate.parents())
 
 
-        e = cmdutil.commiteditor
-        if not opts['message'] and not opts['logfile']:
-            # we don't translate commit messages
-            opts['message'] = "Backed out changeset %s" % short(node)
-            e = cmdutil.commitforceeditor
-
         def commitfunc(ui, repo, message, match, opts):
+            e = cmdutil.commiteditor
+            if not message:
+                # we don't translate commit messages
+                message = "Backed out changeset %s" % short(node)
+                e = cmdutil.commitforceeditor
             return repo.commit(message, opts.get('user'), opts.get('date'),
                                match, editor=e)
         newnode = cmdutil.commit(ui, repo, commitfunc, [], opts)