Re: [PATCH v3 0/4] Speed up unpack_trees()

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 6, 2018, 15:48 UTC
Message-ID: <xmqq7el3qywq.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20180804053723.4695-1-pclouds@gmail.com>

Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:

> This is a minor update to address Ben's comments and add his
> measurements in the commit message of 2/4 for the record.

Yay.

Show 5 quoted lines

> I've also checked about the lookahead thing in unpack_trees() to see
> if we accidentally break something there, which is my biggest worry.
> See [1] and [2] for context, but I believe since we can't have D/F
> conflicts, the situation where lookahead is needed will not occur. So
> we should be safe.

Isn't this about branch switching, where the currently checked out branch may have a regular file 't' and checking out another branch that has directory 't' in it (or vice versa, possibly with the index having either a regular file 't' or requiring 't' to be a diretory by having a blob 't/1' in it)? The log messge of [1] talks about walking three trees together with the index, but even if we limit us to two-tree walk, I do not think that the picture fundamentally changes. So I am not sure how we can confidently say "we can't have D/F". I'd need to block a solid time to take a look at the patches.

> [1] da165f470e (unpack-trees.c: prepare for looking ahead in the index - 2010-01-07)
> [2] 730f72840c (unpack-trees.c: look ahead in the index - 2009-09-20)

Thanks.