Re: [PATCH 2/5] pathspec: add tree_recursive_diff parameter

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 28, 2010, 05:28 UTC
Message-ID: <7vk4m6v3ly.fsf@alter.siamese.dyndns.org>
In-Reply-To: <AANLkTinZt8kish9L2F-ad_boXByZTUj-BnYTp-vtePk0@mail.gmail.com>

Nguyen Thai Ngoc Duy <pclouds@gmail.com> writes:

Show 24 quoted lines

> 2010/9/28 Junio C Hamano <gitster@pobox.com>:
>> Nguyễn Thái Ngọc Duy <pclouds@gmail.com> writes:
>> ...
>>>  - If it's recursive diff, directories are just an intermediate step.
>>>    All path must end with a file name. Thus, directories will be
>>>    unconditionally matched.
>>
>> Hmm, I am not sure what you mean by this.  If the pathspec says a/b*/c,
>> you are in "a" and are deciding if you should descend to its subdirectory,
>> then you would surely want to be able to say:
>>
>>  (1) Ah, the subdirectory I am looking at is "bar" and it does match "b*".
>>      It might contain "c"; I should descend into it.
>>
>>  (2) Nope, the subdirectory I am looking at is "frotz" and it can never
>>      match "b*", so there is no point recursing into it.
>
> I did not go that far, trying to analyse the pattern. When I wrote
> "immediate step" I was thinking of "*foo" pattern, which effectively
> means descending to any reachable directories because '*' matches
> slashes too. I think that's the worst case.
>
> Anyway I did not know that I could borrow some optimizations from
> pathspec_matches() in builtin/grep.c.

As you noticed, over time we have polished our re-implementations of the pathspec logic to avoid needlessly descending into subdirectories, and the one in the grep may be the latest incarnation of it. The logic that uses the path_simplify structure in dir.c may also offer you some inspirations.

Note that the worst case will fall out as a natural consequence of doing the fallback in the dumb and simple way, so you do not have to worry too much about it ;-) I would prefer to see the new, consolidated logic to at least know the easy optimizations we already have.

Thanks.