Fix 3-way-merge of original parent, workdir and new parent.
The dirstate has to match what is in the repository (what would be
checked out with 'hg update -C'), because the resulting file may be
identical to the new parent, or it may be completely different.
Previously the dirstate wasn't updated, so if you changed the file to
look like the original parent, it might be considered unmodified
relative to the new parent.
+ hg init
+ hg add a
+ hg commit -m test -d 0 0
+ hg history
changeset: 0:acb14030fe0a
tag: tip
user: test
date: Thu Jan 1 00:00:00 1970
summary: test
+ hg tag -d 0 0 bleah
+ hg history
changeset: 1:863197ef0378
tag: tip
user: test
date: Thu Jan 1 00:00:00 1970
summary: Added tag bleah for changeset acb14030fe0a21b60322c440ad2d20cf7685a376
changeset: 0:acb14030fe0a
tag: bleah
user: test
date: Thu Jan 1 00:00:00 1970
summary: test
+ hg tag -d 0 0 bleah2
abort: working copy of .hgtags is changed!
(please commit .hgtags manually)
failed