Add a very simple mq test

Avoid extra diffs when not comparing against working dir When diffing against specified revisions expanded keywords only get in the way. Update test output.

Implement support for mq; handle (q)record more gracefully mq: Ensure that expanded keywords do not make it into patches. - disable expansion when reading filelog - shrink expanded keywords when reading from working dir (wread) (q)record: Avoid additional hunks due to expanded keywords. However this is still a compromise, as keyword expansions are not updated in working directory because record should not overwrite files. Mention above shortcomings and "hg kwexpand" workaround in help and update test output. system argument parsing: Command detection might be slightly more expensive with dispatch._parse, but we will need this for improving "hg diff" output.