dispatch: allow extensions to provide setup code we'll need this soon, when record extension will optionally depend on mq early -- when preparing cmdtable. Also, if accepted, ExtensionHowto wiki should be updated as well.

record: refactor record into generic record driver rationale --------- I'd like to make MQ version of record -- qrecord. >From the first glance it seemed to be easy -- the task in essence would be to change call to cmdutil.commit() to something like mq.qrefresh(). As it turned out queue.refresh() and cmdutil.commit() have different semantics -- cmdutil.commit() first scans for changes and then delegate the actual commit to lowlevel func. On the other hand queue.refresh() do it all in once, and I am a bit scary to change it. Maybe the right way would be to first refactor queue.refresh() to use cmdutil.commit() machinery, and then trivially adjust record, but I feel I'm not competent for the task right now. Instead, I propose we refactor record to be some sort of high-level driver, or like a high-level decorator one can say, which will first interactively filter changes, and then delegate commit job to high-level commiter, e.g. 'commit' or 'qrefresh' So, this patch does just that -- refactor record to be generic driver, and update 'hg record' code to use the driver. 'hg qrecord' will follow.

record: some docs While studing record, I've written some docstrings and comments. Hope they are useful.

keyword: clean up quiet setting in kwdemo and adding of untracked kwfiles

keyword: suppress keyword expansion for log commands With previous bugfix "hg log -p" expanded keywords. Turn off again by making log, tip nokwcommands.

keyword: (bugfix) only set changenode for kwtemplater when committing kwexpand must always obtain changenode from filectx, otherwise current changenode is expanded in every file. Also fixes "hg cat <more than 1 file>".

test-mq-header: don't fail with different patch(1) At least under FreeBSD patch(1) won't fail on empty patch and will print 'Hmm...' warning instead. Sanitize output so tests won't fail unexpectedly.