uncommit: add an experimental.uncommitondirtywdir config There are people who wants to do `hg uncommit` on dirty working directory, so this patch adds a config which can be used to the achieve that. Adds tests for the same. Differential Revision: https://phab.mercurial-scm.org/D735

#require docutils gettext

  $ $TESTDIR/check-gendoc el
  checking for parse errors