Re: [Outreachy PATCH] environment: move "core.attributesFile" into repo-setting

>
> When handling multiple repositories within the same process, relying on
> global state for accessing the "core.attributesFile" configuration can
> lead to incorrect values being used. It also makes it harder to isolate
> repositories and hinders the libification of git.
> The functions `bootstrap_attr_stack()` and `git_attr_val_system()`
> retrieve "core.attributesFile" via `git_attr_global_file()`
> which reads from global state `git_attributes_file`.
>
> Move the "core.attributesFile" configuration into the
> `struct repo_settings` instead of relying on the global state.
> A new function `repo_settings_get_attributesfile_path()` is added
> and used to retrieve this setting in a repository-scoped manner.
> The functions to retrieve "core.attributesFile" are replaced with
> the new accessor function `repo_settings_get_attributesfile_path()`
> This improves multi-repository behaviour and aligns with the goal of
> libifying of Git.
>
> Note that in `bootstrap_attr_stack()`, the `index_state` is used only
> if it exists, else we default to `the_repository`.
>
> Based-on-patch-by: Ayush Chandekar <ayu.chandekar@gmail.com>
> Mentored-by: Christian Couder <christian.couder@gmail.com>
> Mentored-by: Usman Akinyemi <usmanakinyemi202@gmail.com>
> Signed-off-by: Olamide Caleb Bello <belkid98@gmail.com>