tests/test-mq-qsave.t

test: add isolated prune case (to test-obsolete-bundle-strip.t)

This adds a test where the prune marker is not related to any other obsmarkers.

  $ 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