submodule: factor out a config_set_in_gitmodules_file_gently function

Introduce a new config_set_in_gitmodules_file_gently() function to write
config values to the .gitmodules file.

This is in preparation for a future change which will use the function
to write to the .gitmodules file in a more controlled way instead of
using "git config -f .gitmodules".

The purpose of the change is mainly to centralize the code that writes
to the .gitmodules file to avoid some duplication.

The naming follows git_config_set_in_file_gently() but the git_ prefix
is removed to communicate that this is not a generic git-config API.

Signed-off-by: Antonio Ospite <ao2@ao2.it>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

submodule-config.c

@@ -707,6 +707,18 @@ int print_config_from_gitmodules(struct repository *repo, const char *key)
 	return 0;
 }
 
+int config_set_in_gitmodules_file_gently(const char *key, const char *value)
+{
+	int ret;
+
+	ret = git_config_set_in_file_gently(GITMODULES_FILE, key, value);
+	if (ret < 0)
+		/* Maybe the user already did that, don't error out here */
+		warning(_("Could not update .gitmodules entry %s"), key);
+
+	return ret;
+}
+
 struct fetch_config {
 	int *max_children;
 	int *recurse_submodules;

submodule-config.h

@@ -49,6 +49,7 @@ const struct submodule *submodule_from_path(struct repository *r,
 					    const char *path);
 void submodule_free(struct repository *r);
 int print_config_from_gitmodules(struct repository *repo, const char *key);
+int config_set_in_gitmodules_file_gently(const char *key, const char *value);
 
 /*
  * Returns 0 if the name is syntactically acceptable as a submodule "name"

submodule.c

@@ -89,6 +89,7 @@ int update_path_in_gitmodules(const char *oldpath, const char *newpath)
 {
 	struct strbuf entry = STRBUF_INIT;
 	const struct submodule *submodule;
+	int ret;
 
 	if (!file_exists(GITMODULES_FILE)) /* Do nothing without .gitmodules */
 		return -1;
@@ -104,14 +105,9 @@ int update_path_in_gitmodules(const char *oldpath, const char *newpath)
 	strbuf_addstr(&entry, "submodule.");
 	strbuf_addstr(&entry, submodule->name);
 	strbuf_addstr(&entry, ".path");
-	if (git_config_set_in_file_gently(GITMODULES_FILE, entry.buf, newpath) < 0) {
-		/* Maybe the user already did that, don't error out here */
-		warning(_("Could not update .gitmodules entry %s"), entry.buf);
-		strbuf_release(&entry);
-		return -1;
-	}
+	ret = config_set_in_gitmodules_file_gently(entry.buf, newpath);
 	strbuf_release(&entry);
-	return 0;
+	return ret;
 }
 
 /*