mq: update .hgsubstate if subrepos are clean (issue2499) This patch prevents MQ from creating an inconsistent subrepo state. If the .hgsub file has been changed, and none of the subrepos have uncommitted changes, creating or updating a patch (using qnew, qrefresh, or qrecord) will update .hgsubstate accordingly. If any subrepos _do_ have uncommitted changes, qnew/qrefresh/qrecord will abort. Thanks to pmezard for proposing this solution.