tests/test-mq-qsave.t

dirstate: rename forget to drop

It has substantially different semantics from forget at the command
layer, so change it to avoid confusion.

We can't simply combine it with remove because we need to explicitly
drop non-added files in some cases like commit.

  $ 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