Merge branch 'ss/submodule-summary-in-c'

Yet another subcommand of "git submodule" is getting rewritten in C.

* ss/submodule-summary-in-c:
  submodule: port submodule subcommand 'summary' from shell to C
  t7421: introduce a test script for verifying 'summary' output
  submodule: rename helper functions to avoid ambiguity
  submodule: remove extra line feeds between callback struct and macro

7 files changed, 512 insertions, 195 deletions

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index a59d8e4bda..b9df79befc 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -612,7 +612,6 @@ struct init_cb {
 	const char *prefix;
 	unsigned int flags;
 };
-
 #define INIT_CB_INIT { NULL, 0 }
 
 static void init_submodule(const char *path, const char *prefix,
@@ -742,7 +741,6 @@ struct status_cb {
 	const char *prefix;
 	unsigned int flags;
 };
-
 #define STATUS_CB_INIT { NULL, 0 }
 
 static void print_status(unsigned int flags, char state, const char *path,
@@ -929,11 +927,438 @@ static int module_name(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+struct module_cb {
+	unsigned int mod_src;
+	unsigned int mod_dst;
+	struct object_id oid_src;
+	struct object_id oid_dst;
+	char status;
+	const char *sm_path;
+};
+#define MODULE_CB_INIT { 0, 0, NULL, NULL, '\0', NULL }
+
+struct module_cb_list {
+	struct module_cb **entries;
+	int alloc, nr;
+};
+#define MODULE_CB_LIST_INIT { NULL, 0, 0 }
+
+struct summary_cb {
+	int argc;
+	const char **argv;
+	const char *prefix;
+	unsigned int cached: 1;
+	unsigned int for_status: 1;
+	unsigned int files: 1;
+	int summary_limit;
+};
+#define SUMMARY_CB_INIT { 0, NULL, NULL, 0, 0, 0, 0 }
+
+enum diff_cmd {
+	DIFF_INDEX,
+	DIFF_FILES
+};
+
+static char* verify_submodule_committish(const char *sm_path,
+					 const char *committish)
+{
+	struct child_process cp_rev_parse = CHILD_PROCESS_INIT;
+	struct strbuf result = STRBUF_INIT;
+
+	cp_rev_parse.git_cmd = 1;
+	cp_rev_parse.dir = sm_path;
+	prepare_submodule_repo_env(&cp_rev_parse.env_array);
+	strvec_pushl(&cp_rev_parse.args, "rev-parse", "-q", "--short", NULL);
+	strvec_pushf(&cp_rev_parse.args, "%s^0", committish);
+	strvec_push(&cp_rev_parse.args, "--");
+
+	if (capture_command(&cp_rev_parse, &result, 0))
+		return NULL;
+
+	strbuf_trim_trailing_newline(&result);
+	return strbuf_detach(&result, NULL);
+}
+
+static void print_submodule_summary(struct summary_cb *info, char* errmsg,
+				    int total_commits, const char *displaypath,
+				    const char *src_abbrev, const char *dst_abbrev,
+				    int missing_src, int missing_dst,
+				    struct module_cb *p)
+{
+	if (p->status == 'T') {
+		if (S_ISGITLINK(p->mod_dst))
+			printf(_("* %s %s(blob)->%s(submodule)"),
+				 displaypath, src_abbrev, dst_abbrev);
+		else
+			printf(_("* %s %s(submodule)->%s(blob)"),
+				 displaypath, src_abbrev, dst_abbrev);
+	} else {
+		printf("* %s %s...%s",
+			displaypath, src_abbrev, dst_abbrev);
+	}
+
+	if (total_commits < 0)
+		printf(":\n");
+	else
+		printf(" (%d):\n", total_commits);
+
+	if (errmsg) {
+		printf(_("%s"), errmsg);
+	} else if (total_commits > 0) {
+		struct child_process cp_log = CHILD_PROCESS_INIT;
+
+		cp_log.git_cmd = 1;
+		cp_log.dir = p->sm_path;
+		prepare_submodule_repo_env(&cp_log.env_array);
+		strvec_pushl(&cp_log.args, "log", NULL);
+
+		if (S_ISGITLINK(p->mod_src) && S_ISGITLINK(p->mod_dst)) {
+			if (info->summary_limit > 0)
+				strvec_pushf(&cp_log.args, "-%d",
+					     info->summary_limit);
+
+			strvec_pushl(&cp_log.args, "--pretty=  %m %s",
+				     "--first-parent", NULL);
+			strvec_pushf(&cp_log.args, "%s...%s",
+				     src_abbrev, dst_abbrev);
+		} else if (S_ISGITLINK(p->mod_dst)) {
+			strvec_pushl(&cp_log.args, "--pretty=  > %s",
+				     "-1", dst_abbrev, NULL);
+		} else {
+			strvec_pushl(&cp_log.args, "--pretty=  < %s",
+				     "-1", src_abbrev, NULL);
+		}
+		run_command(&cp_log);
+	}
+	printf("\n");
+}
+
+static void generate_submodule_summary(struct summary_cb *info,
+				       struct module_cb *p)
+{
+	char *displaypath, *src_abbrev, *dst_abbrev;
+	int missing_src = 0, missing_dst = 0;
+	char *errmsg = NULL;
+	int total_commits = -1;
+
+	if (!info->cached && oideq(&p->oid_dst, &null_oid)) {
+		if (S_ISGITLINK(p->mod_dst)) {
+			struct ref_store *refs = get_submodule_ref_store(p->sm_path);
+			if (refs)
+				refs_head_ref(refs, handle_submodule_head_ref, &p->oid_dst);
+		} else if (S_ISLNK(p->mod_dst) || S_ISREG(p->mod_dst)) {
+			struct stat st;
+			int fd = open(p->sm_path, O_RDONLY);
+
+			if (fd < 0 || fstat(fd, &st) < 0 ||
+			    index_fd(&the_index, &p->oid_dst, fd, &st, OBJ_BLOB,
+				     p->sm_path, 0))
+				error(_("couldn't hash object from '%s'"), p->sm_path);
+		} else {
+			/* for a submodule removal (mode:0000000), don't warn */
+			if (p->mod_dst)
+				warning(_("unexpected mode %d\n"), p->mod_dst);
+		}
+	}
+
+	if (S_ISGITLINK(p->mod_src)) {
+		src_abbrev = verify_submodule_committish(p->sm_path,
+							 oid_to_hex(&p->oid_src));
+		if (!src_abbrev) {
+			missing_src = 1;
+			/*
+			 * As `rev-parse` failed, we fallback to getting
+			 * the abbreviated hash using oid_src. We do
+			 * this as we might still need the abbreviated
+			 * hash in cases like a submodule type change, etc.
+			 */
+			src_abbrev = xstrndup(oid_to_hex(&p->oid_src), 7);
+		}
+	} else {
+		/*
+		 * The source does not point to a submodule.
+		 * So, we fallback to getting the abbreviation using
+		 * oid_src as we might still need the abbreviated
+		 * hash in cases like submodule add, etc.
+		 */
+		src_abbrev = xstrndup(oid_to_hex(&p->oid_src), 7);
+	}
+
+	if (S_ISGITLINK(p->mod_dst)) {
+		dst_abbrev = verify_submodule_committish(p->sm_path,
+							 oid_to_hex(&p->oid_dst));
+		if (!dst_abbrev) {
+			missing_dst = 1;
+			/*
+			 * As `rev-parse` failed, we fallback to getting
+			 * the abbreviated hash using oid_dst. We do
+			 * this as we might still need the abbreviated
+			 * hash in cases like a submodule type change, etc.
+			 */
+			dst_abbrev = xstrndup(oid_to_hex(&p->oid_dst), 7);
+		}
+	} else {
+		/*
+		 * The destination does not point to a submodule.
+		 * So, we fallback to getting the abbreviation using
+		 * oid_dst as we might still need the abbreviated
+		 * hash in cases like a submodule removal, etc.
+		 */
+		dst_abbrev = xstrndup(oid_to_hex(&p->oid_dst), 7);
+	}
+
+	displaypath = get_submodule_displaypath(p->sm_path, info->prefix);
+
+	if (!missing_src && !missing_dst) {
+		struct child_process cp_rev_list = CHILD_PROCESS_INIT;
+		struct strbuf sb_rev_list = STRBUF_INIT;
+
+		strvec_pushl(&cp_rev_list.args, "rev-list",
+			     "--first-parent", "--count", NULL);
+		if (S_ISGITLINK(p->mod_src) && S_ISGITLINK(p->mod_dst))
+			strvec_pushf(&cp_rev_list.args, "%s...%s",
+				     src_abbrev, dst_abbrev);
+		else
+			strvec_push(&cp_rev_list.args, S_ISGITLINK(p->mod_src) ?
+				    src_abbrev : dst_abbrev);
+		strvec_push(&cp_rev_list.args, "--");
+
+		cp_rev_list.git_cmd = 1;
+		cp_rev_list.dir = p->sm_path;
+		prepare_submodule_repo_env(&cp_rev_list.env_array);
+
+		if (!capture_command(&cp_rev_list, &sb_rev_list, 0))
+			total_commits = atoi(sb_rev_list.buf);
+
+		strbuf_release(&sb_rev_list);
+	} else {
+		/*
+		 * Don't give error msg for modification whose dst is not
+		 * submodule, i.e., deleted or changed to blob
+		 */
+		if (S_ISGITLINK(p->mod_dst)) {
+			struct strbuf errmsg_str = STRBUF_INIT;
+			if (missing_src && missing_dst) {
+				strbuf_addf(&errmsg_str, "  Warn: %s doesn't contain commits %s and %s\n",
+					    displaypath, oid_to_hex(&p->oid_src),
+					    oid_to_hex(&p->oid_dst));
+			} else {
+				strbuf_addf(&errmsg_str, "  Warn: %s doesn't contain commit %s\n",
+					    displaypath, missing_src ?
+					    oid_to_hex(&p->oid_src) :
+					    oid_to_hex(&p->oid_dst));
+			}
+			errmsg = strbuf_detach(&errmsg_str, NULL);
+		}
+	}
+
+	print_submodule_summary(info, errmsg, total_commits,
+				displaypath, src_abbrev,
+				dst_abbrev, missing_src,
+				missing_dst, p);
+
+	free(displaypath);
+	free(src_abbrev);
+	free(dst_abbrev);
+}
+
+static void prepare_submodule_summary(struct summary_cb *info,
+				      struct module_cb_list *list)
+{
+	int i;
+	for (i = 0; i < list->nr; i++) {
+		const struct submodule *sub;
+		struct module_cb *p = list->entries[i];
+		struct strbuf sm_gitdir = STRBUF_INIT;
+
+		if (p->status == 'D' || p->status == 'T') {
+			generate_submodule_summary(info, p);
+			continue;
+		}
+
+		if (info->for_status && p->status != 'A' &&
+		    (sub = submodule_from_path(the_repository,
+					       &null_oid, p->sm_path))) {
+			char *config_key = NULL;
+			const char *value;
+			int ignore_all = 0;
+
+			config_key = xstrfmt("submodule.%s.ignore",
+					     sub->name);
+			if (!git_config_get_string_tmp(config_key, &value))
+				ignore_all = !strcmp(value, "all");
+			else if (sub->ignore)
+				ignore_all = !strcmp(sub->ignore, "all");
+
+			free(config_key);
+			if (ignore_all)
+				continue;
+		}
+
+		/* Also show added or modified modules which are checked out */
+		strbuf_addstr(&sm_gitdir, p->sm_path);
+		if (is_nonbare_repository_dir(&sm_gitdir))
+			generate_submodule_summary(info, p);
+		strbuf_release(&sm_gitdir);
+	}
+}
+
+static void submodule_summary_callback(struct diff_queue_struct *q,
+				       struct diff_options *options,
+				       void *data)
+{
+	int i;
+	struct module_cb_list *list = data;
+	for (i = 0; i < q->nr; i++) {
+		struct diff_filepair *p = q->queue[i];
+		struct module_cb *temp;
+
+		if (!S_ISGITLINK(p->one->mode) && !S_ISGITLINK(p->two->mode))
+			continue;
+		temp = (struct module_cb*)malloc(sizeof(struct module_cb));
+		temp->mod_src = p->one->mode;
+		temp->mod_dst = p->two->mode;
+		temp->oid_src = p->one->oid;
+		temp->oid_dst = p->two->oid;
+		temp->status = p->status;
+		temp->sm_path = xstrdup(p->one->path);
+
+		ALLOC_GROW(list->entries, list->nr + 1, list->alloc);
+		list->entries[list->nr++] = temp;
+	}
+}
+
+static const char *get_diff_cmd(enum diff_cmd diff_cmd)
+{
+	switch (diff_cmd) {
+	case DIFF_INDEX: return "diff-index";
+	case DIFF_FILES: return "diff-files";
+	default: BUG("bad diff_cmd value %d", diff_cmd);
+	}
+}
+
+static int compute_summary_module_list(struct object_id *head_oid,
+				       struct summary_cb *info,
+				       enum diff_cmd diff_cmd)
+{
+	struct strvec diff_args = STRVEC_INIT;
+	struct rev_info rev;
+	struct module_cb_list list = MODULE_CB_LIST_INIT;
+
+	strvec_push(&diff_args, get_diff_cmd(diff_cmd));
+	if (info->cached)
+		strvec_push(&diff_args, "--cached");
+	strvec_pushl(&diff_args, "--ignore-submodules=dirty", "--raw", NULL);
+	if (head_oid)
+		strvec_push(&diff_args, oid_to_hex(head_oid));
+	strvec_push(&diff_args, "--");
+	if (info->argc)
+		strvec_pushv(&diff_args, info->argv);
+
+	git_config(git_diff_basic_config, NULL);
+	init_revisions(&rev, info->prefix);
+	rev.abbrev = 0;
+	precompose_argv(diff_args.nr, diff_args.v);
+	setup_revisions(diff_args.nr, diff_args.v, &rev, NULL);
+	rev.diffopt.output_format = DIFF_FORMAT_NO_OUTPUT | DIFF_FORMAT_CALLBACK;
+	rev.diffopt.format_callback = submodule_summary_callback;
+	rev.diffopt.format_callback_data = &list;
+
+	if (!info->cached) {
+		if (diff_cmd == DIFF_INDEX)
+			setup_work_tree();
+		if (read_cache_preload(&rev.diffopt.pathspec) < 0) {
+			perror("read_cache_preload");
+			return -1;
+		}
+	} else if (read_cache() < 0) {
+		perror("read_cache");
+		return -1;
+	}
+
+	if (diff_cmd == DIFF_INDEX)
+		run_diff_index(&rev, info->cached);
+	else
+		run_diff_files(&rev, 0);
+	prepare_submodule_summary(info, &list);
+	strvec_clear(&diff_args);
+	return 0;
+}
+
+static int module_summary(int argc, const char **argv, const char *prefix)
+{
+	struct summary_cb info = SUMMARY_CB_INIT;
+	int cached = 0;
+	int for_status = 0;
+	int files = 0;
+	int summary_limit = -1;
+	enum diff_cmd diff_cmd = DIFF_INDEX;
+	struct object_id head_oid;
+	int ret;
+
+	struct option module_summary_options[] = {
+		OPT_BOOL(0, "cached", &cached,
+			 N_("use the commit stored in the index instead of the submodule HEAD")),
+		OPT_BOOL(0, "files", &files,
+			 N_("to compare the commit in the index with that in the submodule HEAD")),
+		OPT_BOOL(0, "for-status", &for_status,
+			 N_("skip submodules with 'ignore_config' value set to 'all'")),
+		OPT_INTEGER('n', "summary-limit", &summary_limit,
+			     N_("limit the summary size")),
+		OPT_END()
+	};
+
+	const char *const git_submodule_helper_usage[] = {
+		N_("git submodule--helper summary [<options>] [commit] [--] [<path>]"),
+		NULL
+	};
+
+	argc = parse_options(argc, argv, prefix, module_summary_options,
+			     git_submodule_helper_usage, 0);
+
+	if (!summary_limit)
+		return 0;
+
+	if (!get_oid(argc ? argv[0] : "HEAD", &head_oid)) {
+		if (argc) {
+			argv++;
+			argc--;
+		}
+	} else if (!argc || !strcmp(argv[0], "HEAD")) {
+		/* before the first commit: compare with an empty tree */
+		oidcpy(&head_oid, the_hash_algo->empty_tree);
+		if (argc) {
+			argv++;
+			argc--;
+		}
+	} else {
+		if (get_oid("HEAD", &head_oid))
+			die(_("could not fetch a revision for HEAD"));
+	}
+
+	if (files) {
+		if (cached)
+			die(_("--cached and --files are mutually exclusive"));
+		diff_cmd = DIFF_FILES;
+	}
+
+	info.argc = argc;
+	info.argv = argv;
+	info.prefix = prefix;
+	info.cached = !!cached;
+	info.files = !!files;
+	info.for_status = !!for_status;
+	info.summary_limit = summary_limit;
+
+	ret = compute_summary_module_list((diff_cmd == DIFF_INDEX) ? &head_oid : NULL,
+					  &info, diff_cmd);
+	return ret;
+}
+
 struct sync_cb {
 	const char *prefix;
 	unsigned int flags;
 };
-
 #define SYNC_CB_INIT { NULL, 0 }
 
 static void sync_submodule(const char *path, const char *prefix,
@@ -2344,6 +2769,7 @@ static struct cmd_struct commands[] = {
 	{"print-default-remote", print_default_remote, 0},
 	{"sync", module_sync, SUPPORT_SUPER_PREFIX},
 	{"deinit", module_deinit, 0},
+	{"summary", module_summary, SUPPORT_SUPER_PREFIX},
 	{"remote-branch", resolve_remote_submodule_branch, 0},
 	{"push-check", push_check, 0},
 	{"absorb-git-dirs", absorb_git_dirs, SUPPORT_SUPER_PREFIX},
diff --git a/diff.c b/diff.c
index 0299a73079..a5114fa864 100644
--- a/diff.c
+++ b/diff.c
@@ -3432,7 +3432,7 @@ static void builtin_diff(const char *name_a,
 	if (o->submodule_format == DIFF_SUBMODULE_LOG &&
 	    (!one->mode || S_ISGITLINK(one->mode)) &&
 	    (!two->mode || S_ISGITLINK(two->mode))) {
-		show_submodule_summary(o, one->path ? one->path : two->path,
+		show_submodule_diff_summary(o, one->path ? one->path : two->path,
 				&one->oid, &two->oid,
 				two->dirty_submodule);
 		return;
diff --git a/git-submodule.sh b/git-submodule.sh
index 43eb6051d2..6fb12585cb 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -59,31 +59,6 @@ die_if_unmatched ()
 	fi
 }
 
-#
-# Print a submodule configuration setting
-#
-# $1 = submodule name
-# $2 = option name
-# $3 = default value
-#
-# Checks in the usual git-config places first (for overrides),
-# otherwise it falls back on .gitmodules.  This allows you to
-# distribute project-wide defaults in .gitmodules, while still
-# customizing individual repositories if necessary.  If the option is
-# not in .gitmodules either, print a default value.
-#
-get_submodule_config () {
-	name="$1"
-	option="$2"
-	default="$3"
-	value=$(git config submodule."$name"."$option")
-	if test -z "$value"
-	then
-		value=$(git submodule--helper config submodule."$name"."$option")
-	fi
-	printf '%s' "${value:-$default}"
-}
-
 isnumber()
 {
 	n=$(($1 + 0)) 2>/dev/null && test "$n" = "$1"
@@ -831,166 +806,7 @@ cmd_summary() {
 		shift
 	done
 
-	test $summary_limit = 0 && return
-
-	if rev=$(git rev-parse -q --verify --default HEAD ${1+"$1"})
-	then
-		head=$rev
-		test $# = 0 || shift
-	elif test -z "$1" || test "$1" = "HEAD"
-	then
-		# before the first commit: compare with an empty tree
-		head=$(git hash-object -w -t tree --stdin </dev/null)
-		test -z "$1" || shift
-	else
-		head="HEAD"
-	fi
-
-	if [ -n "$files" ]
-	then
-		test -n "$cached" &&
-		die "$(gettext "The --cached option cannot be used with the --files option")"
-		diff_cmd=diff-files
-		head=
-	fi
-
-	cd_to_toplevel
-	eval "set $(git rev-parse --sq --prefix "$wt_prefix" -- "$@")"
-	# Get modified modules cared by user
-	modules=$(git $diff_cmd $cached --ignore-submodules=dirty --raw $head -- "$@" |
-		sane_egrep '^:([0-7]* )?160000' |
-		while read -r mod_src mod_dst sha1_src sha1_dst status sm_path
-		do
-			# Always show modules deleted or type-changed (blob<->module)
-			if test "$status" = D || test "$status" = T
-			then
-				printf '%s\n' "$sm_path"
-				continue
-			fi
-			# Respect the ignore setting for --for-status.
-			if test -n "$for_status"
-			then
-				name=$(git submodule--helper name "$sm_path")
-				ignore_config=$(get_submodule_config "$name" ignore none)
-				test $status != A && test $ignore_config = all && continue
-			fi
-			# Also show added or modified modules which are checked out
-			GIT_DIR="$sm_path/.git" git rev-parse --git-dir >/dev/null 2>&1 &&
-			printf '%s\n' "$sm_path"
-		done
-	)
-
-	test -z "$modules" && return
-
-	git $diff_cmd $cached --ignore-submodules=dirty --raw $head -- $modules |
-	sane_egrep '^:([0-7]* )?160000' |
-	cut -c2- |
-	while read -r mod_src mod_dst sha1_src sha1_dst status name
-	do
-		if test -z "$cached" &&
-			is_zero_oid $sha1_dst
-		then
-			case "$mod_dst" in
-			160000)
-				sha1_dst=$(GIT_DIR="$name/.git" git rev-parse HEAD)
-				;;
-			100644 | 100755 | 120000)
-				sha1_dst=$(git hash-object $name)
-				;;
-			000000)
-				;; # removed
-			*)
-				# unexpected type
-				eval_gettextln "unexpected mode \$mod_dst" >&2
-				continue ;;
-			esac
-		fi
-		missing_src=
-		missing_dst=
-
-		test $mod_src = 160000 &&
-		! GIT_DIR="$name/.git" git rev-parse -q --verify $sha1_src^0 >/dev/null &&
-		missing_src=t
-
-		test $mod_dst = 160000 &&
-		! GIT_DIR="$name/.git" git rev-parse -q --verify $sha1_dst^0 >/dev/null &&
-		missing_dst=t
-
-		display_name=$(git submodule--helper relative-path "$name" "$wt_prefix")
-
-		total_commits=
-		case "$missing_src,$missing_dst" in
-		t,)
-			errmsg="$(eval_gettext "  Warn: \$display_name doesn't contain commit \$sha1_src")"
-			;;
-		,t)
-			errmsg="$(eval_gettext "  Warn: \$display_name doesn't contain commit \$sha1_dst")"
-			;;
-		t,t)
-			errmsg="$(eval_gettext "  Warn: \$display_name doesn't contain commits \$sha1_src and \$sha1_dst")"
-			;;
-		*)
-			errmsg=
-			total_commits=$(
-			if test $mod_src = 160000 && test $mod_dst = 160000
-			then
-				range="$sha1_src...$sha1_dst"
-			elif test $mod_src = 160000
-			then
-				range=$sha1_src
-			else
-				range=$sha1_dst
-			fi
-			GIT_DIR="$name/.git" \
-			git rev-list --first-parent $range -- | wc -l
-			)
-			total_commits=" ($(($total_commits + 0)))"
-			;;
-		esac
-
-		sha1_abbr_src=$(GIT_DIR="$name/.git" git rev-parse --short $sha1_src 2>/dev/null ||
-			echo $sha1_src | cut -c1-7)
-		sha1_abbr_dst=$(GIT_DIR="$name/.git" git rev-parse --short $sha1_dst 2>/dev/null ||
-			echo $sha1_dst | cut -c1-7)
-
-		if test $status = T
-		then
-			blob="$(gettext "blob")"
-			submodule="$(gettext "submodule")"
-			if test $mod_dst = 160000
-			then
-				echo "* $display_name $sha1_abbr_src($blob)->$sha1_abbr_dst($submodule)$total_commits:"
-			else
-				echo "* $display_name $sha1_abbr_src($submodule)->$sha1_abbr_dst($blob)$total_commits:"
-			fi
-		else
-			echo "* $display_name $sha1_abbr_src...$sha1_abbr_dst$total_commits:"
-		fi
-		if test -n "$errmsg"
-		then
-			# Don't give error msg for modification whose dst is not submodule
-			# i.e. deleted or changed to blob
-			test $mod_dst = 160000 && echo "$errmsg"
-		else
-			if test $mod_src = 160000 && test $mod_dst = 160000
-			then
-				limit=
-				test $summary_limit -gt 0 && limit="-$summary_limit"
-				GIT_DIR="$name/.git" \
-				git log $limit --pretty='format:  %m %s' \
-				--first-parent $sha1_src...$sha1_dst
-			elif test $mod_dst = 160000
-			then
-				GIT_DIR="$name/.git" \
-				git log --pretty='format:  > %s' -1 $sha1_dst
-			else
-				GIT_DIR="$name/.git" \
-				git log --pretty='format:  < %s' -1 $sha1_src
-			fi
-			echo
-		fi
-		echo
-	done
+	git ${wt_prefix:+-C "$wt_prefix"} submodule--helper summary ${prefix:+--prefix "$prefix"} ${files:+--files} ${cached:+--cached} ${for_status:+--for-status} ${summary_limit:+-n $summary_limit} -- "$@"
 }
 #
 # List all submodules, prefixed with:
diff --git a/submodule.c b/submodule.c
index 3cbcf40dfc..6f8002fc9e 100644
--- a/submodule.c
+++ b/submodule.c
@@ -438,7 +438,7 @@ void handle_ignore_submodules_arg(struct diff_options *diffopt,
 	 */
 }
 
-static int prepare_submodule_summary(struct rev_info *rev, const char *path,
+static int prepare_submodule_diff_summary(struct rev_info *rev, const char *path,
 		struct commit *left, struct commit *right,
 		struct commit_list *merge_bases)
 {
@@ -459,7 +459,7 @@ static int prepare_submodule_summary(struct rev_info *rev, const char *path,
 	return prepare_revision_walk(rev);
 }
 
-static void print_submodule_summary(struct repository *r, struct rev_info *rev, struct diff_options *o)
+static void print_submodule_diff_summary(struct repository *r, struct rev_info *rev, struct diff_options *o)
 {
 	static const char format[] = "  %m %s";
 	struct strbuf sb = STRBUF_INIT;
@@ -610,7 +610,7 @@ output_header:
 	strbuf_release(&sb);
 }
 
-void show_submodule_summary(struct diff_options *o, const char *path,
+void show_submodule_diff_summary(struct diff_options *o, const char *path,
 		struct object_id *one, struct object_id *two,
 		unsigned dirty_submodule)
 {
@@ -632,12 +632,12 @@ void show_submodule_summary(struct diff_options *o, const char *path,
 		goto out;
 
 	/* Treat revision walker failure the same as missing commits */
-	if (prepare_submodule_summary(&rev, path, left, right, merge_bases)) {
+	if (prepare_submodule_diff_summary(&rev, path, left, right, merge_bases)) {
 		diff_emit_submodule_error(o, "(revision walker failed)\n");
 		goto out;
 	}
 
-	print_submodule_summary(sub, &rev, o);
+	print_submodule_diff_summary(sub, &rev, o);
 
 out:
 	if (merge_bases)
diff --git a/submodule.h b/submodule.h
index 9ce85c03fe..4ac6e31cf1 100644
--- a/submodule.h
+++ b/submodule.h
@@ -69,7 +69,7 @@ int parse_submodule_update_strategy(const char *value,
 				    struct submodule_update_strategy *dst);
 const char *submodule_strategy_to_string(const struct submodule_update_strategy *s);
 void handle_ignore_submodules_arg(struct diff_options *, const char *);
-void show_submodule_summary(struct diff_options *o, const char *path,
+void show_submodule_diff_summary(struct diff_options *o, const char *path,
 			    struct object_id *one, struct object_id *two,
 			    unsigned dirty_submodule);
 void show_submodule_inline_diff(struct diff_options *o, const char *path,
diff --git a/t/t7401-submodule-summary.sh b/t/t7401-submodule-summary.sh
index cc87d26619..7608814708 100755
--- a/t/t7401-submodule-summary.sh
+++ b/t/t7401-submodule-summary.sh
@@ -7,6 +7,12 @@ test_description='Summary support for submodules
 
 This test script tries to verify the sanity of summary subcommand of git submodule.
 '
+
+# NOTE: This test script uses 'git add' instead of 'git submodule add' to add
+# submodules to the superproject. Some submodule subcommands such as init and
+# deinit might not work as expected in this script. t7421 does not have this
+# caveat.
+#
 # NEEDSWORK: This test script is old fashioned and may need a big cleanup due to
 # various reasons, one of them being that there are lots of commands taking place
 # outside of 'test_expect_success' block, which is no longer in good-style.
diff --git a/t/t7421-submodule-summary-add.sh b/t/t7421-submodule-summary-add.sh
new file mode 100755
index 0000000000..59a9b00467
--- /dev/null
+++ b/t/t7421-submodule-summary-add.sh
@@ -0,0 +1,69 @@
+#!/bin/sh
+#
+# Copyright (C) 2020 Shourya Shukla
+#
+
+test_description='Summary support for submodules, adding them using git submodule add
+
+This test script tries to verify the sanity of summary subcommand of git submodule
+while making sure to add submodules using `git submodule add` instead of
+`git add` as done in t7401.
+'
+
+. ./test-lib.sh
+
+test_expect_success 'summary test environment setup' '
+	git init sm &&
+	test_commit -C sm "add file" file file-content file-tag &&
+
+	git submodule add ./sm my-subm &&
+	test_tick &&
+	git commit -m "add submodule"
+'
+
+test_expect_success 'submodule summary output for initialized submodule' '
+	test_commit -C sm "add file2" file2 file2-content file2-tag &&
+	git submodule update --remote &&
+	test_tick &&
+	git commit -m "update submodule" my-subm &&
+	git submodule summary HEAD^ >actual &&
+	rev1=$(git -C sm rev-parse --short HEAD^) &&
+	rev2=$(git -C sm rev-parse --short HEAD) &&
+	cat >expected <<-EOF &&
+	* my-subm ${rev1}...${rev2} (1):
+	  > add file2
+
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'submodule summary output for deinitialized submodule' '
+	git submodule deinit my-subm &&
+	git submodule summary HEAD^ >actual &&
+	test_must_be_empty actual &&
+	git submodule update --init my-subm &&
+	git submodule summary HEAD^ >actual &&
+	rev1=$(git -C sm rev-parse --short HEAD^) &&
+	rev2=$(git -C sm rev-parse --short HEAD) &&
+	cat >expected <<-EOF &&
+	* my-subm ${rev1}...${rev2} (1):
+	  > add file2
+
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'submodule summary output for submodules with changed paths' '
+	git mv my-subm subm &&
+	git commit -m "change submodule path" &&
+	rev=$(git -C sm rev-parse --short HEAD^) &&
+	git submodule summary HEAD^^ -- my-subm >actual 2>err &&
+	grep "fatal:.*my-subm" err &&
+	cat >expected <<-EOF &&
+	* my-subm ${rev}...0000000:
+
+	EOF
+	test_cmp expected actual
+'
+
+test_done