git submodule update: Introduce --recursive to update nested submodules

In very large and hierarchically structured projects, one may encounter
nested submodules. In these situations, it is valuable to not only update
the submodules in the current repo (which is what is currently done by
'git submodule update'), but also to operate on all submodules at all
levels (i.e. recursing into nested submodules as well).

This patch teaches the new --recursive option to the 'git submodule update'
command. The patch also includes documentation and selftests.

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-submodule.txt

@@ -14,7 +14,7 @@ SYNOPSIS
 'git submodule' [--quiet] status [--cached] [--] [<path>...]
 'git submodule' [--quiet] init [--] [<path>...]
 'git submodule' [--quiet] update [--init] [-N|--no-fetch] [--rebase]
-	      [--reference <repository>] [--merge] [--] [<path>...]
+	      [--reference <repository>] [--merge] [--recursive] [--] [<path>...]
 'git submodule' [--quiet] summary [--cached] [--summary-limit <n>] [commit] [--] [<path>...]
 'git submodule' [--quiet] foreach [--recursive] <command>
 'git submodule' [--quiet] sync [--] [<path>...]
@@ -122,6 +122,9 @@ update::
 If the submodule is not yet initialized, and you just want to use the
 setting as stored in .gitmodules, you can automatically initialize the
 submodule with the --init option.
++
+If '--recursive' is specified, this command will recurse into the
+registered submodules, and update any nested submodules within.
 
 summary::
 	Show commit summary between the given commit (defaults to HEAD) and
@@ -213,7 +216,7 @@ OPTIONS
 for linkgit:git-clone[1]'s --reference and --shared options carefully.
 
 --recursive::
-	This option is only valid for the foreach command.
+	This option is only valid for foreach and update commands.
 	Traverse submodules recursively. The operation is performed not
 	only in the submodules of the current repo, but also
 	in any nested submodules inside those submodules (and so on).

git-submodule.sh

@@ -8,7 +8,7 @@ dashless=$(basename "$0" | sed -e 's/-/ /')
 USAGE="[--quiet] add [-b branch] [--reference <repository>] [--] <repository> <path>
    or: $dashless [--quiet] status [--cached] [--] [<path>...]
    or: $dashless [--quiet] init [--] [<path>...]
-   or: $dashless [--quiet] update [--init] [-N|--no-fetch] [--rebase] [--reference <repository>] [--merge] [--] [<path>...]
+   or: $dashless [--quiet] update [--init] [-N|--no-fetch] [--rebase] [--reference <repository>] [--merge] [--recursive] [--] [<path>...]
    or: $dashless [--quiet] summary [--cached] [--summary-limit <n>] [commit] [--] [<path>...]
    or: $dashless [--quiet] foreach [--recursive] <command>
    or: $dashless [--quiet] sync [--] [<path>...]"
@@ -352,6 +352,7 @@ cmd_init()
 cmd_update()
 {
 	# parse $args after "submodule ... update".
+	orig_args="$@"
 	while test $# -ne 0
 	do
 		case "$1" in
@@ -384,6 +385,10 @@ cmd_update()
 			shift
 			update="merge"
 			;;
+		--recursive)
+			shift
+			recursive=1
+			;;
 		--)
 			shift
 			break
@@ -470,6 +475,12 @@ cmd_update()
 			die "Unable to $action '$sha1' in submodule path '$path'"
 			say "Submodule path '$path': $msg '$sha1'"
 		fi
+
+		if test -n "$recursive"
+		then
+			(unset GIT_DIR; cd "$path" && cmd_update $orig_args) ||
+			die "Failed to recurse into submodule path '$path'"
+		fi
 	done
 }
 

t/t7407-submodule-foreach.sh

@@ -175,4 +175,23 @@ test_expect_success 'test "foreach --quiet --recursive"' '
 	test_cmp expect actual
 '
 
+test_expect_success 'use "update --recursive" to checkout all submodules' '
+	git clone super clone3 &&
+	(
+		cd clone3 &&
+		test ! -d sub1/.git &&
+		test ! -d sub2/.git &&
+		test ! -d sub3/.git &&
+		test ! -d nested1/.git &&
+		git submodule update --init --recursive &&
+		test -d sub1/.git &&
+		test -d sub2/.git &&
+		test -d sub3/.git &&
+		test -d nested1/.git &&
+		test -d nested1/nested2/.git &&
+		test -d nested1/nested2/nested3/.git &&
+		test -d nested1/nested2/nested3/submodule/.git
+	)
+'
+
 test_done