config: rename git_etc_config()

The `git_etc_gitconfig()` function retrieves the system-level path of
the configuration file. We're about to introduce a way to override it
via an environment variable, at which point the name of this function
would start to become misleading.

Rename the function to `git_system_config()` as a preparatory step.
While at it, the function is also refactored to pass memory ownership to
the caller. This is done to better match semantics of
`git_global_config()`, which is going to be introduced in the next
commit.

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

builtin/config.c

@@ -695,7 +695,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		}
 	}
 	else if (use_system_config) {
-		given_config_source.file = git_etc_gitconfig();
+		given_config_source.file = git_system_config();
 		given_config_source.scope = CONFIG_SCOPE_SYSTEM;
 	} else if (use_local_config) {
 		given_config_source.file = git_pathdup("config");

config.c

@@ -1844,12 +1844,9 @@ static int git_config_from_blob_ref(config_fn_t fn,
 	return git_config_from_blob_oid(fn, name, &oid, data);
 }
 
-const char *git_etc_gitconfig(void)
+char *git_system_config(void)
 {
-	static const char *system_wide;
-	if (!system_wide)
-		system_wide = system_path(ETC_GITCONFIG);
-	return system_wide;
+	return system_path(ETC_GITCONFIG);
 }
 
 /*
@@ -1883,6 +1880,7 @@ static int do_git_config_sequence(const struct config_options *opts,
 				  config_fn_t fn, void *data)
 {
 	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 *repo_config;
@@ -1896,11 +1894,10 @@ static int do_git_config_sequence(const struct config_options *opts,
 		repo_config = NULL;
 
 	current_parsing_scope = CONFIG_SCOPE_SYSTEM;
-	if (git_config_system() && !access_or_die(git_etc_gitconfig(), R_OK,
-						  opts->system_gently ?
-						  ACCESS_EACCES_OK : 0))
-		ret += git_config_from_file(fn, git_etc_gitconfig(),
-					    data);
+	if (git_config_system() && system_config &&
+	    !access_or_die(system_config, R_OK,
+			   opts->system_gently ? ACCESS_EACCES_OK : 0))
+		ret += git_config_from_file(fn, system_config, data);
 
 	current_parsing_scope = CONFIG_SCOPE_GLOBAL;
 	if (xdg_config && !access_or_die(xdg_config, R_OK, ACCESS_EACCES_OK))
@@ -1927,6 +1924,7 @@ static int do_git_config_sequence(const struct config_options *opts,
 		die(_("unable to parse command-line config"));
 
 	current_parsing_scope = prev_parsing_scope;
+	free(system_config);
 	free(xdg_config);
 	free(user_config);
 	free(repo_config);

config.h

@@ -318,7 +318,6 @@ int git_config_rename_section(const char *, const char *);
 int git_config_rename_section_in_file(const char *, const char *, const char *);
 int git_config_copy_section(const char *, const char *);
 int git_config_copy_section_in_file(const char *, const char *, const char *);
-const char *git_etc_gitconfig(void);
 int git_env_bool(const char *, int);
 unsigned long git_env_ulong(const char *, unsigned long);
 int git_config_system(void);
@@ -327,6 +326,8 @@ int config_error_nonbool(const char *);
 #define config_error_nonbool(s) (config_error_nonbool(s), const_error())
 #endif
 
+char *git_system_config(void);
+
 int git_config_parse_parameter(const char *, config_fn_t fn, void *data);
 
 enum config_scope current_config_scope(void);