tests/test-mq-qsave.t

test: add test for a former race resulting in bad dirstate

In 6.0 this used to result in the size being stored in the dirstate is wrong.
This was fixed by other change to the mtime gathering logic.

Differential Revision: https://phab.mercurial-scm.org/D11749

  $ 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