subrepo: bare git repos considered dirty
Currently, if there is a bare git subrepo, but it is at the "right"
revision, calling dirty() will error because diff-index does not work
on bare repos. This patch makes it so bare subrepos are always
considered dirty.
Issue351: mq: qrefresh can create extra revlog entry
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ hg qinit
$ echo b > b
$ hg ci -A -m foo
adding b
$ echo cc > b
$ hg qnew -f foo.diff
$ echo b > b
$ hg qrefresh
$ hg debugindex b
rev offset length base linkrev nodeid p1 p2
0 0 3 0 0 1e88685f5dde 000000000000 000000000000