[GSoC] [PATCH] submodule--helper: introduce add-config subcommand

[Atharva Raykar <raykar.ath@gmail.com>]

Add a new "add-config" subcommand to `git submodule--helper` with the
goal of converting part of the shell code in git-submodule.sh related to
`git submodule add` into C code. This new subcommand sets the
configuration variables of a newly added submodule, by registering the
url in local git config, as well as the submodule name and path in the
.gitmodules file. It also sets 'submodule.<name>.active' to "true" if
the submodule path has not already been covered by any pathspec
specified in 'submodule.active'.

This is meant to be a faithful conversion from shell to C, with only one
minor change: A warning is emitted if no value is specified in
'submodule.active', ie, the config looks like: "[submodule] active\n",
because it is an invalid configuration. It would be helpful to let the
user know that the pathspec is unset, and the value of
'submodule.<name>.active' might be set to 'true' so that they can
rectify their configuration and prevent future surprises (especially
given that the latter variable has a higher priority than the former).

The structure of the conditional to check if we need to set the 'active'
toggle looks different from the shell version -- but behaves the same.
The change was made to decrease code duplication. A comment has been
added to explain that only one value of 'submodule.active' is obtained
to check if we need to call is_submodule_active() at all.

Signed-off-by: Atharva Raykar <raykar.ath@gmail.com>
Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Shourya Shukla <periperidip@gmail.com>
Based-on-patch-by: Shourya Shukla <periperidip@gmail.com>
Based-on-patch-by: Prathamesh Chavan <pc44800@gmail.com>
---

This patch depends on changes introduced in 83913dd5b6 (t7400: test failure to
add submodule in tracked path, 2021-06-18), which belongs to the
ar/submodule-add (2021-07-12) series[1].

This changes in this patch are no different from the one in my first
submodule-add conversion series[2] which has already got some reviews before.

[1] https://lore.kernel.org/git/20210710074801.19917-1-raykar.ath@gmail.com/
[2] https://lore.kernel.org/git/20210615145745.33382-4-raykar.ath@gmail.com/

 builtin/submodule--helper.c | 125 ++++++++++++++++++++++++++++++++++++
 git-submodule.sh            |  28 +-------
 2 files changed, 126 insertions(+), 27 deletions(-)

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 862053c9f2..9658804d24 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -2936,6 +2936,130 @@ static int add_clone(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+static void config_submodule_in_gitmodules(const char *name, const char *var, const char *value)
+{
+	char *key;
+
+	if (!is_writing_gitmodules_ok())
+		die(_("please make sure that the .gitmodules file is in the working tree"));
+
+	key = xstrfmt("submodule.%s.%s", name, var);
+	config_set_in_gitmodules_file_gently(key, value);
+	free(key);
+}
+
+static void configure_added_submodule(struct add_data *add_data)
+{
+	char *key, *submod_pathspec = NULL;
+	struct child_process add_submod = CHILD_PROCESS_INIT;
+	struct child_process add_gitmodules = CHILD_PROCESS_INIT;
+	int pathspec_key_exists, activate = 0;
+
+	key = xstrfmt("submodule.%s.url", add_data->sm_name);
+	git_config_set_gently(key, add_data->realrepo);
+	free(key);
+
+	add_submod.git_cmd = 1;
+	strvec_pushl(&add_submod.args, "add",
+		     "--no-warn-embedded-repo", NULL);
+	if (add_data->force)
+		strvec_push(&add_submod.args, "--force");
+	strvec_pushl(&add_submod.args, "--", add_data->sm_path, NULL);
+
+	if (run_command(&add_submod))
+		die(_("Failed to add submodule '%s'"), add_data->sm_path);
+
+	config_submodule_in_gitmodules(add_data->sm_name, "path", add_data->sm_path);
+	config_submodule_in_gitmodules(add_data->sm_name, "url", add_data->repo);
+	if (add_data->branch)
+		config_submodule_in_gitmodules(add_data->sm_name,
+					       "branch", add_data->branch);
+
+	add_gitmodules.git_cmd = 1;
+	strvec_pushl(&add_gitmodules.args,
+		     "add", "--force", "--", ".gitmodules", NULL);
+
+	if (run_command(&add_gitmodules))
+		die(_("Failed to register submodule '%s'"), add_data->sm_path);
+
+	/*
+	 * NEEDSWORK: In a multi-working-tree world this needs to be
+	 * set in the per-worktree config.
+	 */
+	pathspec_key_exists = !git_config_get_string("submodule.active",
+						     &submod_pathspec);
+	if (pathspec_key_exists && !submod_pathspec) {
+		warning(_("The submodule.active configuration exists, but the "
+			  "pathspec was unset. If the submodule is not already "
+			  "active, the value of submodule.%s.active will be "
+			  "be set to 'true'."), add_data->sm_name);
+		activate = 1;
+	}
+
+	/*
+	 * If submodule.active does not exist, or if the pathspec was unset,
+	 * we will activate this module unconditionally.
+	 *
+	 * Otherwise, we ask is_submodule_active(), which iterates
+	 * through all the values of 'submodule.active' to determine
+	 * if this module is already active.
+	 */
+	if (!pathspec_key_exists || activate ||
+	    !is_submodule_active(the_repository, add_data->sm_path)) {
+		key = xstrfmt("submodule.%s.active", add_data->sm_name);
+		git_config_set_gently(key, "true");
+		free(key);
+	}
+}
+
+static int add_config(int argc, const char **argv, const char *prefix)
+{
+	int force = 0;
+	struct add_data add_data = ADD_DATA_INIT;
+
+	struct option options[] = {
+		OPT_STRING('b', "branch", &add_data.branch,
+			   N_("branch"),
+			   N_("branch of repository to store in "
+			      "the submodule configuration")),
+		OPT_STRING(0, "url", &add_data.repo,
+			   N_("string"),
+			   N_("url to clone submodule from")),
+		OPT_STRING(0, "resolved-url", &add_data.realrepo,
+			   N_("string"),
+			   N_("url to clone the submodule from, after it has "
+			      "been dereferenced relative to parent's url, "
+			      "in the case where <url> is a relative url")),
+		OPT_STRING(0, "path", &add_data.sm_path,
+			   N_("path"),
+			   N_("where the new submodule will be cloned to")),
+		OPT_STRING(0, "name", &add_data.sm_name,
+			   N_("string"),
+			   N_("name of the new submodule")),
+		OPT__FORCE(&force, N_("allow adding an otherwise ignored submodule path"),
+			   PARSE_OPT_NOCOMPLETE),
+		OPT_END()
+	};
+
+	const char *const usage[] = {
+		N_("git submodule--helper add-config "
+		   "[--force|-f] [--branch|-b <branch>] "
+		   "--url <url> --resolved-url <resolved-url> "
+		   "--path <path> --name <name>"),
+		NULL
+	};
+
+	argc = parse_options(argc, argv, prefix, options, usage, 0);
+
+	if (argc != 0)
+		usage_with_options(usage, options);
+
+	add_data.force = !!force;
+	configure_added_submodule(&add_data);
+
+	return 0;
+}
+
 #define SUPPORT_SUPER_PREFIX (1<<0)
 
 struct cmd_struct {
@@ -2949,6 +3073,7 @@ static struct cmd_struct commands[] = {
 	{"name", module_name, 0},
 	{"clone", module_clone, 0},
 	{"add-clone", add_clone, 0},
+	{"add-config", add_config, 0},
 	{"update-module-mode", module_update_module_mode, 0},
 	{"update-clone", update_clone, 0},
 	{"ensure-core-worktree", ensure_core_worktree, 0},
diff --git a/git-submodule.sh b/git-submodule.sh
index 053daf3724..f713cb113c 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -242,33 +242,7 @@ cmd_add()
 	fi
 
 	git submodule--helper add-clone ${GIT_QUIET:+--quiet} ${force:+"--force"} ${progress:+"--progress"} ${branch:+--branch "$branch"} --prefix "$wt_prefix" --path "$sm_path" --name "$sm_name" --url "$realrepo" ${reference:+"$reference"} ${dissociate:+"--dissociate"} ${depth:+"$depth"} || exit
-	git config submodule."$sm_name".url "$realrepo"
-
-	git add --no-warn-embedded-repo $force "$sm_path" ||
-	die "fatal: $(eval_gettext "Failed to add submodule '\$sm_path'")"
-
-	git submodule--helper config submodule."$sm_name".path "$sm_path" &&
-	git submodule--helper config submodule."$sm_name".url "$repo" &&
-	if test -n "$branch"
-	then
-		git submodule--helper config submodule."$sm_name".branch "$branch"
-	fi &&
-	git add --force .gitmodules ||
-	die "fatal: $(eval_gettext "Failed to register submodule '\$sm_path'")"
-
-	# NEEDSWORK: In a multi-working-tree world, this needs to be
-	# set in the per-worktree config.
-	if git config --get submodule.active >/dev/null
-	then
-		# If the submodule being adding isn't already covered by the
-		# current configured pathspec, set the submodule's active flag
-		if ! git submodule--helper is-active "$sm_path"
-		then
-			git config submodule."$sm_name".active "true"
-		fi
-	else
-		git config submodule."$sm_name".active "true"
-	fi
+	git submodule--helper add-config ${force:+--force} ${branch:+--branch "$branch"} --url "$repo" --resolved-url "$realrepo" --path "$sm_path" --name "$sm_name"
 }
 
 #
-- 
2.32.0