Subject: Re: [RFC PATCH] config: teach `repo_config()` to allow `repo` to be NULL

From: Junio C Hamano <[email-masked]>
Date: Thu, 27 Feb 2025 10:46:11 -0800

Usman Akinyemi <[email-masked]> writes:

> The `repo` value can be NULL if a builtin command is run outside
> any repository. The current implementation of `repo_config()` will
> fail if `repo` is NULL.
>
> If the `repo` is NULL the `repo_config()` can ignore the repository
> configuration but it should read the other configuration sources like
> the system-side configuration instead of failing.
>
> Teach the `repo_config()` to allow `repo` to be NULL by calling the
> `read_very_early_config()` which read config but only enumerate system
> and global settings.
>
> Suggested-by: Junio C Hamano <[email-masked]>
> Mentored-by: Christian Couder <[email-masked]>
> Signed-off-by: Usman Akinyemi <[email-masked]>
> ---
>  config.c | 4 ++++
>  config.h | 3 +++
>  2 files changed, 7 insertions(+)

Thanks for tackling this one.  The other day I was looking at the
code paths involved and was trying to think of a way to "fix" it at
deeper level than this one, but didn't think of this much simpler
solution.

This is so drastic a change of behaviour that it deserves some
tests, I think.

> diff --git a/config.c b/config.c
> index 36f76fafe5..c5181fd23b 100644
> --- a/config.c
> +++ b/config.c
> @@ -2526,6 +2526,10 @@ void repo_config_clear(struct repository *repo)
>  
>  void repo_config(struct repository *repo, config_fn_t fn, void *data)
>  {
> +	if (!repo) {
> +		read_very_early_config(fn, data);
> +		return;
> +	}
>  	git_config_check_init(repo);
>  	configset_iter(repo->config, fn, data);
>  }
> diff --git a/config.h b/config.h
> index 5c730c4f89..1e5b22dfc4 100644
> --- a/config.h
> +++ b/config.h
> @@ -219,6 +219,9 @@ void read_very_early_config(config_fn_t cb, void *data);
>   * repo-specific one; by overwriting, the higher-priority repo-specific
>   * value is left at the end).
>   *
> + * In cases where the repository variable is NULL, repo_config() will
> + * call read_early_config().
> + *
>   * Unlike git_config_from_file(), this function respects includes.
>   */
>  void repo_config(struct repository *r, config_fn_t fn, void *);