[GSoC] [PATCH v3] 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, although we
add comments to areas that could be improved in future patches, after
the conversion has settled.

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>
---

Changes since v2:

* Change the commit message, which erroneously still spoke about a warning that
  has since been removed.

* Change the structure of the code that checks if a submodule is active, so that
  it more closely resembles the conditional in the original shell version, and
  preserves the original comments.

* Add NEEDSWORK comments, one to state the future intention of removing the
  check for 'submodule.active' before anyway calling is_submodule_active().
  The other comment is to state the intention of adding a warning in a future
  patch when 'is_submodule_active()' reads a valueless 'submodule.active'.

Fetch-it-via:
git fetch https://github.com/tfidfwastaken/git.git submodule-helper-add-config-3

 builtin/submodule--helper.c | 128 ++++++++++++++++++++++++++++++++++++
 git-submodule.sh            |  28 +-------
 submodule.c                 |   5 ++
 3 files changed, 134 insertions(+), 27 deletions(-)

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 862053c9f2..791ceeb63e 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -2936,6 +2936,133 @@ static int add_clone(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+static int config_submodule_in_gitmodules(const char *name, const char *var, const char *value)
+{
+	char *key;
+	int ret;
+
+	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);
+	ret = config_set_in_gitmodules_file_gently(key, value);
+	free(key);
+
+	return ret;
+}
+
+static void configure_added_submodule(struct add_data *add_data)
+{
+	char *key;
+	char *val = NULL;
+	struct child_process add_submod = CHILD_PROCESS_INIT;
+	struct child_process add_gitmodules = CHILD_PROCESS_INIT;
+
+	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);
+
+	if (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))
+		die(_("Failed to register submodule '%s'"), add_data->sm_path);
+
+	if (add_data->branch)
+		if (config_submodule_in_gitmodules(add_data->sm_name,
+						   "branch", add_data->branch))
+			die(_("Failed to register submodule '%s'"), add_data->sm_path);
+
+	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.
+	 */
+	/*
+	 * NEEDSWORK: In the longer run, we need to get rid of this
+	 * pattern of querying "submodule.active" before calling
+	 * is_submodule_active(), since that function needs to find
+	 * out the value of "submodule.active" again anyway.
+	 */
+	if (!git_config_get_string("submodule.active", &val) && val) {
+		/*
+		 * If the submodule being added isn't already covered by the
+		 * current configured pathspec, set the submodule's active flag
+		 */
+		if (!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);
+		}
+	} else {
+		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)
+		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 +3076,7 @@ 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"
 }
 
 #
diff --git a/submodule.c b/submodule.c
index 0b1d9c1dde..8577667773 100644
--- a/submodule.c
+++ b/submodule.c
@@ -237,6 +237,11 @@ int option_parse_recurse_submodules_worktree_updater(const struct option *opt,
 /*
  * Determine if a submodule has been initialized at a given 'path'
  */
+/*
+ * NEEDSWORK: Emit a warning if submodule.active exists, but is valueless,
+ * ie, the config looks like: "[submodule] active\n".
+ * Since that is an invalid pathspec, we should inform the user.
+ */
 int is_submodule_active(struct repository *repo, const char *path)
 {
 	int ret = 0;
-- 
2.32.0