Subject: Re: [RFC PATCH 1/1] mv: integrate with sparse-index

From: Junio C Hamano <[email-masked]>
Date: Mon, 21 Mar 2022 12:14:36 -0700

Derrick Stolee <[email-masked]> writes:

>>> Another tool that may help you here is 'git ls-files --sparse -t'. It lists
>>> the files in the index and their "tags" ('H' is "normal" tracked files, 'S'
>>> is SKIP_WORKTREE, etc. [4]), which can help identify when a file you'd
>>> expect to be SKIP_WORKTREE is not and vice versa.
>> 
>> Wonderful.
>> 
>> Quite honestly, because the code will most likely compile correctly
>> if you just remove the unconditional "we first expand the in-core
>> index fully" code, and because the "sparse index" makes the existing
>> index walking code fail in unexpected and surprising ways, I
>> consider it unsuitably harder for people who are not yet familiar
>> with the system.  Without a good test coverage (which is hard to
>> give unless you are familiar with the code being tested X-<), one
>> can easily get confused and lost.
>
> Certainly, 'git mv' is looking to be harder than expected, but there
> is a lot of interesting exploration happening in the process.

Yeah, I know.

I am suprised that it is harder than expected *to* *you*, though.
After having seen a few other topics, I thought that you should know
how deceptively easy to lose "require-full" and how hard to audit
the code that may expect "a flat list of paths" in the in-core index
;-).

> Thanks for persisting on this one, Shaoxuan!

Yes, thanks.  And thanks for mentoring Shaoxuan.