Merge branch 'fg/submodule-clone-depth'

Allow shallow-cloning of submodules with "git submodule update".

* fg/submodule-clone-depth:
  Add --depth to submodule update/add

git-submodule.sh

@@ -35,6 +35,7 @@ nofetch=
 update=
 prefix=
 custom_name=
+depth=
 
 # The function takes at most 2 arguments. The first argument is the
 # URL that navigates to the submodule origin repo. When relative, this URL
@@ -251,6 +252,7 @@ module_clone()
 	name=$2
 	url=$3
 	reference="$4"
+	depth="$5"
 	quiet=
 	if test -n "$GIT_QUIET"
 	then
@@ -273,7 +275,7 @@ module_clone()
 		mkdir -p "$gitdir_base"
 		(
 			clear_local_git_env
-			git clone $quiet -n ${reference:+"$reference"} \
+			git clone $quiet ${depth:+"$depth"} -n ${reference:+"$reference"} \
 				--separate-git-dir "$gitdir" "$url" "$sm_path"
 		) ||
 		die "$(eval_gettext "Clone of '\$url' into submodule path '\$sm_path' failed")"
@@ -350,6 +352,14 @@ cmd_add()
 			custom_name=$2
 			shift
 			;;
+		--depth)
+			case "$2" in '') usage ;; esac
+			depth="--depth=$2"
+			shift
+			;;
+		--depth=*)
+			depth=$1
+			;;
 		--)
 			shift
 			break
@@ -459,7 +469,7 @@ Use -f if you really want to add it." >&2
 				echo "$(eval_gettext "Reactivating local git directory for submodule '\$sm_name'.")"
 			fi
 		fi
-		module_clone "$sm_path" "$sm_name" "$realrepo" "$reference" || exit
+		module_clone "$sm_path" "$sm_name" "$realrepo" "$reference" "$depth" || exit
 		(
 			clear_local_git_env
 			cd "$sm_path" &&
@@ -736,6 +746,14 @@ cmd_update()
 		--checkout)
 			update="checkout"
 			;;
+		--depth)
+			case "$2" in '') usage ;; esac
+			depth="--depth=$2"
+			shift
+			;;
+		--depth=*)
+			depth=$1
+			;;
 		--)
 			shift
 			break
@@ -797,7 +815,7 @@ Maybe you want to use 'update --init'?")"
 
 		if ! test -d "$sm_path"/.git -o -f "$sm_path"/.git
 		then
-			module_clone "$sm_path" "$name" "$url" "$reference" || exit
+			module_clone "$sm_path" "$name" "$url" "$reference" "$depth" || exit
 			cloned_modules="$cloned_modules;$name"
 			subsha1=
 		else