tests/readlink.py

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).

#!/usr/bin/env python

import errno, os, sys

for f in sys.argv[1:]:
    try:
        print f, '->', os.readlink(f)
    except OSError, err:
        if err.errno != errno.EINVAL:
            raise
        print f, 'not a symlink'

sys.exit(0)