Re: [PATCH v4 0/3] config: allow overriding global/system config

> Compared to v3, I only dropped the special-casing of `/dev/null`. As
> Junio rightly pointed out, the special-casing was incomplete and would
> have required more work to do the right thing for all cases. It can
> still be re-added at a later point if the usecase actually comes up.
>
> Patrick
>
> Patrick Steinhardt (3):
>   config: rename `git_etc_config()`
>   config: unify code paths to get global config paths
>   config: allow overriding of global and system configuration
>
>  Documentation/git-config.txt |  5 +++
>  Documentation/git.txt        | 10 +++++
>  builtin/config.c             |  6 +--
>  config.c                     | 41 +++++++++++++++------
>  config.h                     |  4 +-
>  t/t1300-config.sh            | 71 ++++++++++++++++++++++++++++++++++++
>  6 files changed, 121 insertions(+), 16 deletions(-)

>
> Range-diff against v3:
> 1:  34bdbc27d6 = 1:  34bdbc27d6 config: rename `git_etc_config()`
> 2:  30f18679bd = 2:  30f18679bd config: unify code paths to get global config paths
> 3:  af663640ae ! 3:  d27efc0aa8 config: allow overriding of global and system configuration
>     @@ Commit message
>              - If unset, git continues to use the usual locations.
>      
>              - If set to a specific path, we skip reading the normal
>     -          configuration files and instead take the path.
>     -
>     -        - If set to `/dev/null`, we do not load either global- or
>     -          system-level configuration at all.
>     +          configuration files and instead take the path. By setting the path
>     +          to `/dev/null`, no configuration will be loaded for the respective
>     +          level.
>      
>          This implements the usecase where we want to execute code in a sanitized
>          environment without any potential misconfigurations via `/dev/null`, but
>     @@ Documentation/git.txt: for further details.
>       	Whether to skip reading settings from the system-wide
>       	`$(prefix)/etc/gitconfig` file.  This environment variable can
>      
>     - ## builtin/config.c ##
>     -@@ builtin/config.c: int cmd_config(int argc, const char **argv, const char *prefix)
>     - 		char *user_config, *xdg_config;
>     - 
>     - 		git_global_config(&user_config, &xdg_config);
>     --		if (!user_config)
>     -+		if (!user_config) {
>     -+			if (getenv("GIT_CONFIG_GLOBAL"))
>     -+				die(_("GIT_CONFIG_GLOBAL=/dev/null set"));
>     -+
>     - 			/*
>     - 			 * It is unknown if HOME/.gitconfig exists, so
>     - 			 * we do not know if we should write to XDG
>     -@@ builtin/config.c: int cmd_config(int argc, const char **argv, const char *prefix)
>     - 			 * is set and points at a sane location.
>     - 			 */
>     - 			die(_("$HOME not set"));
>     -+		}
>     - 
>     - 		given_config_source.scope = CONFIG_SCOPE_GLOBAL;
>     - 
>     -
>       ## config.c ##
>      @@ config.c: static int git_config_from_blob_ref(config_fn_t fn,
>       
>       char *git_system_config(void)
>       {
>      +	char *system_config = xstrdup_or_null(getenv("GIT_CONFIG_SYSTEM"));
>     -+	if (system_config) {
>     -+		if (!strcmp(system_config, "/dev/null"))
>     -+			FREE_AND_NULL(system_config);
>     ++	if (system_config)
>      +		return system_config;
>     -+	}
>       	return system_path(ETC_GITCONFIG);
>       }
>       
>     @@ config.c: static int git_config_from_blob_ref(config_fn_t fn,
>      +	char *user_config = xstrdup_or_null(getenv("GIT_CONFIG_GLOBAL"));
>      +	char *xdg_config = NULL;
>      +
>     -+	if (user_config) {
>     -+		if (!strcmp(user_config, "/dev/null"))
>     -+			FREE_AND_NULL(user_config);
>     -+		xdg_config = NULL;
>     -+	} else {
>     ++	if (!user_config) {
>      +		user_config = expand_user_path("~/.gitconfig", 0);
>      +		xdg_config = xdg_config_home("config");
>      +	}