[PATCH 2/4] submodule: implement `module_name` as a builtin helper

[Stefan Beller <sbeller@google.com>]

The goal of this series being rewriting `git submodule update`,
we don't want to call out to the shell script for config lookups.

So reimplement the lookup of the submodule name in C.

Signed-off-by: Stefan Beller <sbeller@google.com>
---

 When I started to implement git submodule add in the helper, I realized
 the very first thing to be done would be module_name translated to C,
 so I did that separately. Maybe we need to split this up as well into two
 separate steps for processing and I/O, such that it can be reused better
 from a future "git submodule--helper update" function

 builtin/submodule--helper.c | 47 +++++++++++++++++++++++++++++++++++++++++++++
 git-submodule.sh            | 32 +++++++-----------------------
 2 files changed, 54 insertions(+), 25 deletions(-)

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index cb18ddf..dd5635f 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -5,6 +5,8 @@
 #include "pathspec.h"
 #include "dir.h"
 #include "utf8.h"
+#include "run-command.h"
+#include "string-list.h"
 
 static char *ps_matched;
 static const struct cache_entry **ce_entries;
@@ -98,6 +100,48 @@ static int module_list(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+
+static int collect_module_names(const char *key, const char *value, void *cb)
+{
+	size_t len;
+	struct string_list *sl = cb;
+
+	if (starts_with(key, "submodule.")
+	    && strip_suffix(key, ".path", &len)) {
+		struct strbuf sb = STRBUF_INIT;
+		strbuf_add(&sb, key + strlen("submodule."),
+				len - strlen("submodule."));
+		string_list_insert(sl, value)->util = strbuf_detach(&sb, NULL);
+		strbuf_release(&sb);
+	}
+
+	return 0;
+}
+
+static int module_name(int argc, const char **argv, const char *prefix)
+{
+	struct string_list_item *item;
+	struct git_config_source config_source;
+	struct string_list values = STRING_LIST_INIT_DUP;
+
+	if (!argc)
+		usage("git submodule--helper module_name <path>\n");
+
+	memset(&config_source, 0, sizeof(config_source));
+	config_source.file = ".gitmodules";
+
+	if (git_config_with_options(collect_module_names, &values,
+				    &config_source, 1) < 0)
+		die(_("unknown error occured while reading the git modules file"));
+
+	item = string_list_lookup(&values, argv[0]);
+	if (item)
+		printf("%s\n", (char*)item->util);
+	else
+		die("No submodule mapping found in .gitmodules for path '%s'", argv[0]);
+	return 0;
+}
+
 int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
 {
 	if (argc < 2)
@@ -106,6 +150,9 @@ int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
 	if (!strcmp(argv[1], "module_list"))
 		return module_list(argc - 1, argv + 1, prefix);
 
+	if (!strcmp(argv[1], "module_name"))
+		return module_name(argc - 2, argv + 2, prefix);
+
 usage:
 	usage("git submodule--helper module_list\n");
 }
diff --git a/git-submodule.sh b/git-submodule.sh
index af9ecef..e6ff38d 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -178,24 +178,6 @@ get_submodule_config () {
 	printf '%s' "${value:-$default}"
 }
 
-
-#
-# Map submodule path to submodule name
-#
-# $1 = path
-#
-module_name()
-{
-	# Do we have "submodule.<something>.path = $1" defined in .gitmodules file?
-	sm_path="$1"
-	re=$(printf '%s\n' "$1" | sed -e 's/[].[^$\\*]/\\&/g')
-	name=$( git config -f .gitmodules --get-regexp '^submodule\..*\.path$' |
-		sed -n -e 's|^submodule\.\(.*\)\.path '"$re"'$|\1|p' )
-	test -z "$name" &&
-	die "$(eval_gettext "No submodule mapping found in .gitmodules for path '\$sm_path'")"
-	printf '%s\n' "$name"
-}
-
 #
 # Clone a submodule
 #
@@ -498,7 +480,7 @@ cmd_foreach()
 		then
 			displaypath=$(relative_path "$sm_path")
 			say "$(eval_gettext "Entering '\$prefix\$displaypath'")"
-			name=$(module_name "$sm_path")
+			name=$(git submodule--helper module_name "$sm_path")
 			(
 				prefix="$prefix$sm_path/"
 				clear_local_git_env
@@ -554,7 +536,7 @@ cmd_init()
 	while read mode sha1 stage sm_path
 	do
 		die_if_unmatched "$mode"
-		name=$(module_name "$sm_path") || exit
+		name=$(git submodule--helper module_name "$sm_path") || exit
 
 		displaypath=$(relative_path "$sm_path")
 
@@ -636,7 +618,7 @@ cmd_deinit()
 	while read mode sha1 stage sm_path
 	do
 		die_if_unmatched "$mode"
-		name=$(module_name "$sm_path") || exit
+		name=$(git submodule--helper module_name "$sm_path") || exit
 
 		displaypath=$(relative_path "$sm_path")
 
@@ -758,7 +740,7 @@ cmd_update()
 			echo >&2 "Skipping unmerged submodule $prefix$sm_path"
 			continue
 		fi
-		name=$(module_name "$sm_path") || exit
+		name=$(git submodule--helper module_name "$sm_path") || exit
 		url=$(git config submodule."$name".url)
 		branch=$(get_submodule_config "$name" branch master)
 		if ! test -z "$update"
@@ -1022,7 +1004,7 @@ cmd_summary() {
 			# Respect the ignore setting for --for-status.
 			if test -n "$for_status"
 			then
-				name=$(module_name "$sm_path")
+				name=$(git submodule--helper module_name "$sm_path")
 				ignore_config=$(get_submodule_config "$name" ignore none)
 				test $status != A && test $ignore_config = all && continue
 			fi
@@ -1184,7 +1166,7 @@ cmd_status()
 	while read mode sha1 stage sm_path
 	do
 		die_if_unmatched "$mode"
-		name=$(module_name "$sm_path") || exit
+		name=$(git submodule--helper module_name "$sm_path") || exit
 		url=$(git config submodule."$name".url)
 		displaypath=$(relative_path "$prefix$sm_path")
 		if test "$stage" = U
@@ -1261,7 +1243,7 @@ cmd_sync()
 	while read mode sha1 stage sm_path
 	do
 		die_if_unmatched "$mode"
-		name=$(module_name "$sm_path")
+		name=$(git submodule--helper module_name "$sm_path")
 		url=$(git config -f .gitmodules --get submodule."$name".url)
 
 		# Possibly a url relative to parent
-- 
2.5.0.2.gbb9888f.dirty