shelve: handle shelved node on unfiltered repository
To build a version of shelve that use hiding instead of stripping, we need
shelve to be able to find these revisions. This it does not hurt the bundle
version, so we introduce the necessary code in the relevant place.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state