config: unify code paths to get global config paths

There's two callsites which assemble global config paths, once in the
config loading code and once in the git-config(1) builtin. We're about
to implement a way to override global config paths via an environment
variable which would require us to adjust both sites.

Unify both code paths into a single `git_global_config()` function which
returns both paths for `~/.gitconfig` and the XDG config file. This will
make the subsequent patch which introduces the new envvar easier to
implement.

No functional changes are expected from this patch.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/config.c

@@ -671,9 +671,9 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 	}
 
 	if (use_global_config) {
-		char *user_config = expand_user_path("~/.gitconfig", 0);
-		char *xdg_config = xdg_config_home("config");
+		char *user_config, *xdg_config;
 
+		git_global_config(&user_config, &xdg_config);
 		if (!user_config)
 			/*
 			 * It is unknown if HOME/.gitconfig exists, so

config.c

@@ -1849,6 +1849,12 @@ char *git_system_config(void)
 	return system_path(ETC_GITCONFIG);
 }
 
+void git_global_config(char **user_config, char **xdg_config)
+{
+	*user_config = expand_user_path("~/.gitconfig", 0);
+	*xdg_config = xdg_config_home("config");
+}
+
 /*
  * Parse environment variable 'k' as a boolean (in various
  * possible spellings); if missing, use the default value 'def'.
@@ -1881,8 +1887,8 @@ static int do_git_config_sequence(const struct config_options *opts,
 {
 	int ret = 0;
 	char *system_config = git_system_config();
-	char *xdg_config = xdg_config_home("config");
-	char *user_config = expand_user_path("~/.gitconfig", 0);
+	char *xdg_config = NULL;
+	char *user_config = NULL;
 	char *repo_config;
 	enum config_scope prev_parsing_scope = current_parsing_scope;
 
@@ -1900,6 +1906,8 @@ static int do_git_config_sequence(const struct config_options *opts,
 		ret += git_config_from_file(fn, system_config, data);
 
 	current_parsing_scope = CONFIG_SCOPE_GLOBAL;
+	git_global_config(&user_config, &xdg_config);
+
 	if (xdg_config && !access_or_die(xdg_config, R_OK, ACCESS_EACCES_OK))
 		ret += git_config_from_file(fn, xdg_config, data);
 

config.h

@@ -327,6 +327,7 @@ int config_error_nonbool(const char *);
 #endif
 
 char *git_system_config(void);
+void git_global_config(char **user, char **xdg);
 
 int git_config_parse_parameter(const char *, config_fn_t fn, void *data);