import: use dirstateguard instead of dirstate.invalidate
Before this patch, "commands.import()" 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" at failure even if "dirstate.write()" is
executed before failure.
This patch also removes "beginparentchage()" and "endparentchange()",
because "dirstateguard" makes them useless, too.
This is a part of preparations to fix the issue that the recent (in
memory) dirstate isn't visible to external process (e.g. "precommit"
hook).
$ hg init
$ echo a > a
$ hg ci -Am t
adding a
$ hg mv a b
$ hg ci -Am t1
$ hg debugrename b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3
$ hg mv b a
$ hg ci -Am t2
$ hg debugrename a
a renamed from b:37d9b5d994eab34eda9c16b195ace52c7b129980
$ hg debugrename --rev 1 b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3