rhg: Group values passed to every sub-command into a struct
The set of which values this is is evidently not stable yet,
so this will make changes easier. Also it is growing, and the function
signatures are getting out hand.
Differential Revision: https://phab.mercurial-scm.org/D10003
#require docutils gettext
$ $TESTDIR/check-gendoc zh_CN
checking for parse errors