tests/test-issue1438.t

mq: use dirstateguard instead of dirstate.invalidate (qrefresh)

Before this patch, "mq.queue.refresh()" uses "dirstate.invalidate()"
as a kind of "restore .hg/dirstate to the original status" during a failure.

But it just discards changes in memory, and doesn't actually restore
".hg/dirstate". Then, it can't work as expected, if "dirstate.write()"
is executed while processing.

This patch uses "dirstateguard" instead of "dirstate.invalidate()" to
restore ".hg/dirstate" during a failure even if "dirstate.write()" is
executed before a failure.

This patch also removes "beginparentchage()" and "endparentchange()",
because "dirstateguard" makes them useless.

This is a part of preparations to fix the issue that the recent (in
memory) dirstate isn't visible to external processes (e.g. "precommit"
hook).

#require symlink

http://mercurial.selenic.com/bts/issue1438

  $ hg init

  $ ln -s foo link
  $ hg add link
  $ hg ci -mbad link
  $ hg rm link
  $ hg ci -mok
  $ hg diff -g -r 0:1 > bad.patch

  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg import --no-commit bad.patch
  applying bad.patch

  $ hg status
  R link
  ? bad.patch