Re: [PATCH 2/2] give exclude mechanism a debug option

> Users can set GIT_DEBUG_IGNORE in the environment to get the
> exclusion mechanism to dump to stderr files mentioned in
> .gitignore along with the pattern that matched. The output
> looks something like:
>
>   foo.c: exclude: *.c
>
> This implementation has several shortcomings that make it
> unsuitable for inclusion:
>
>   1. Doing it as a debug environment variable is hack-ish.
>      A nicer interface would be a .gitignore equivalent of
>      "git check-attr".

>   2. If you ask for "foo/bar", and "foo/" is ignored, the
>      output will show only "foo: exclude: foo". This is an
>      artifact of the calling interface: you don't ask "is
>      foo/bar excluded", but rather while recursing through
>      "foo/" you ask "should I bother even recursing into
>      foo?". So the exclusion code never even knows that you
>      might have cared about foo/bar in the first place.

>   3. There is no indication of where patterns came from. We
>      could specify whether it came from the command-line,
>      from per-directory files, or from another file. But what
>      is most interesting is the actual _filename_ that it
>      came from. I.e., something like:
>
>        sub/foo.c: exclude: sub/.gitignore: *.c
>
>      But that information seems to have been forgotten by
>      the time we are actually doing excludes.