Re: [PATCH 1/3] git-gui: move into "subprojects/"

> The "git-gui" project has recently gained support for being built with
> Meson, but it is not yet wired up in Git's own Meson build instructions.
> "git-gui" itself is wired up as a standalone project, which means that
> we can trivially make it available via `subproject("git-gui")`.
>
> So far the theory. In practice thoguh the `subproject()` function comes

> with a couple of limitations. Most importantly, all subprojects need to
> be contained in the same directory, and that directory cannot be the
> top-level directory of the parent project. Right now we use the default
> subproject directory ("subprojects/") for a couple of fallbacks in case
> some important dependencies couldn't be found.
>
> This means that we cannot just include the "git-gui" directory as a
> subproject as it lives in our root directory. There are three options:
>
>   - We move "git-gui" into "subprojects/". It requires a bit of churn,
>     but should otherwise not have any significant downsides.
>
>   - We create a symlink pointing from "subprojects/git-gui" to the
>     top-level directory. This may not work on Windows.
>
>   - We can create a "git-gui.wrap" file that knows to pull a specific
>     commit from upstream and build it. This would mean that Meson and
>     Makefiles now have different sources of truth for which version of
>     "git-gui" we build.
>
> The first option feels like the most sensible solution. It creates churn
> and requires us to adapt the pull-request workflow a bit. But this
> should be a one-time cost.
>
> In theory we could also rename the "subprojects/" directory by passing
> the "subproject_dir" argument to our `project()` call. But the name
> feels quite fitting for our purpose, as well.
>