Re: [PATCH v2 6/6] exclude: filter patterns by directory level

> Junio C Hamano <gitster@pobox.com> writes:
>
>> Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:
>>
>>> A non-basename pattern that does not contain /**/ can't match anything
>>> outside the attached directory. Record its directory level and avoid
>>> matching unless the pathname is also at the same directory level.
>>
>> Without defining what a "directory level" is, the above is a bit
>> hard to grok, but I think you mean an entry "b/c/*.c" that appears
>> in "a/.gitignore" file will want to match a path that is directly
>> in "a/b/c" directory (and not in its subdirectories),
>> "a/b/x.c" at the two levels deep subdirectory or "a/b/c/d/x.c" that is
>> four levels deep will never match the pattern.
>>
>> The logic feels sound.
>
> Actually, I think you may be able to do a lot more with a simpler
> change.  If your top-level .gitignore has "a/b/c/*.c" in it, you
> certainly want to mark it not to be applied when you are looking at
> paths directly in directory a/b/ because they will never match, but
> you also know that nothing will match when you are inside a/b/d/,
> even though the pattern and the path you are checking are at the
> same levels.  Your dirlen approach will fail for that case, no?
>
> The idea behind prep_exclude() that organizes the exclode patterns
> into a stack structure and update the groups near the leaves by
> popping those for the old directory we were in and pushing those for
> the new directory we are going into is to give us a place to tweak
> the elements on the whole stack for optimization when we notice that
> we are looking at paths in different directories.  Instead of giving
> a "dirlen" member to each element, you could give a "do not look at
> me" flag to it, and when you notice that you were in a/b/c/ and now
> you are going to look at paths in a/b/d/, you can look at the group
> that was read from the .gitignore from the top-level, and mark
> entries that cannot be relevant (e.g. "a/b/c/*.c") as such.
>
> The mark does not have to be a boolean.  "a/b/*.c" when you are in
> "a/b/c/" can be marked as "This never matches, and I do not have to
> re-check until I pop one level".  When digging deeper to "a/b/c/d",
> you add one to that.  When switching to "a/b/e", you would first pop
> twice ("d" and then "c"), each time decrementing the "I do not have
> to re-check" counter by one, and then when pushing "e" down, you
> notice that you need to re-check, and mark it again as "no need to
> re-check for one pop".  So it is not like you have to re-scan all
> entries textually every time you switch directories. Most entries
> that are level-limited you would increment or decrement its counter
> and only the ones at the level boundary need to be re-checked.