Re: [RFC] extending pathspec support to submodules

[Brandon Williams <bmwill@google.com>]

On Thu, Sep 15, 2016 at 4:57 AM, Heiko Voigt <hvoigt@hvoigt.net> wrote:
>
> The problem when you do that is that the child is not aware that it is
> actually run as a submodule process. E.g.
>
>    git grep --recurse-submodules foobar -- sub/dir/a
>
> would report back matches in 'dir/a' instead of 'sub/dir/a'. From the
> users perspective this will be confusing since she started the grep in
> the superproject.
>
> So what I would suggest is that we make the childs aware of the fact
> that they are called from a superproject by passing a prefix when
> calling it. E.g. like this
>
>    git grep --submodule-prefix=sub foobar -- sub/dir/a
>
> Whether we pass the full or stripped path is now a matter of taste or
> ease of implementation, since we could either preprend or strip it in
> the child. But the important difference is that we have information
> about the original path.
>
> Another approach could, of course, be to omit passing the prefix and
> parse the output of the child and try to substitute, paths but that
> seems quite error prone to me.
>
> Cheers Heiko

You're right that seems like the best course of action and it already falls
inline with what I did with a first patch to ls-files to support submodules.
In that patch I did exactly as you suggest and pass in the prefix to the
submodule and make the child responsible for prepending the prefix to all of
its output.  This way we can simply pass through the whole pathspec (as apposed
to my original idea of stripping the prefix off the pathspec prior to passing
it to the child...which can get complicated with wild characters) to the
childprocess and when checking if a file matches the pathspec we can check if
the prefix + file path matches.

-Brandon