keyword: support 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.