From: Junio C Hamano <gitster@pobox•com>
To: Duy Nguyen <pclouds@gmail•com>
Cc: Michael J Gruber <git@drmicha•warpmail.net>,
Git Mailing List <git@vger•kernel.org>
Subject: Re: [PATCH v2] diff-lib.c: adjust position of i-t-a entries in diff
Date: Tue, 24 Mar 2015 10:00:43 -0700 [thread overview]
Message-ID: <xmqqtwxa72kk.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <CACsJy8BczCNxm3WHK1gtkXiZCbDkFD-67oOMR+eK8uwOBfQXuw@mail.gmail.com> (Duy Nguyen's message of "Tue, 24 Mar 2015 08:15:50 +0700")
Duy Nguyen <pclouds@gmail•com> writes:
> "read-tree -m" does not invoke diff, does it? If I went with my
> previous approach (modifying unpack-trees to ignore i-t-a entries)
> then this could be a problem, but because unpack-trees is untouched,
> merge operations should not be impacted by this patch.
Theoretically yes, but not quite.
I wouldn't be surprised if an enterprising soul saw an optimization
opportunity in the "read-tree -m A B" codepath. When it finds that
a tree in A and a valid cache-tree entry that corresponds to the
tree matches, it could blow away all index entries covered by the
cache-tree entry and replace them with B, either
(1) unconditionally when "-u" is not given; or
(2) as long as the working tree matches the index inside that
directory when running with "-u".
And such an optimization used to be a valid thing to do in the old
world; but (1) will break in the new world, if we drop that
invalidation---the i-t-a entries will be discarded from the index.
As i-t-a is not a norm but an abberration, I'd rather keep the
pessimizing invalidation to keep the door open for such an
optimization for a more common case, and there may be other cases
in which our correctness around i-t-a depends on.
next prev parent reply other threads:[~2015-03-24 17:51 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-09 14:14 [PATCH/RFC 0/2] Bug fixes regarding diff and "git add -N" Nguyễn Thái Ngọc Duy
2015-03-09 14:14 ` [PATCH 1/2] diff --cached: do not report i-t-a entries as "new" Nguyễn Thái Ngọc Duy
2015-03-15 6:55 ` Junio C Hamano
2015-03-16 13:56 ` [PATCH v2] diff-lib.c: adjust position of i-t-a entries in diff Nguyễn Thái Ngọc Duy
2015-03-16 15:15 ` Michael J Gruber
2015-03-16 16:05 ` Junio C Hamano
2015-03-17 14:07 ` Duy Nguyen
2015-03-17 17:57 ` Junio C Hamano
2015-03-18 12:47 ` Duy Nguyen
2015-03-18 20:30 ` Junio C Hamano
2015-03-19 6:00 ` Junio C Hamano
2015-03-24 1:15 ` Duy Nguyen
2015-03-24 17:00 ` Junio C Hamano [this message]
2015-03-23 20:52 ` Junio C Hamano
2015-03-09 14:14 ` [PATCH 2/2] diff-files: mark i-t-a paths as "new" Nguyễn Thái Ngọc Duy
2015-03-15 7:05 ` Junio C Hamano
2015-03-09 15:45 ` [PATCH] t2203,t4011: adjust to changed intent-to-add treatment Michael J Gruber
2015-03-15 7:07 ` Junio C Hamano
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