Merge branch 'ba/clone-remote-submodules'

"git clone --recurse-submodules" learned to set up the submodules
to ignore commit object names recorded in the superproject gitlink
and instead use the commits that happen to be at the tip of the
remote-tracking branches from the get-go, by passing the new
"--remote-submodules" option.

* ba/clone-remote-submodules:
  clone: add `--remote-submodules` flag

Documentation/git-clone.txt

@@ -15,7 +15,8 @@ SYNOPSIS
 	  [--dissociate] [--separate-git-dir <git dir>]
 	  [--depth <depth>] [--[no-]single-branch] [--no-tags]
 	  [--recurse-submodules[=<pathspec>]] [--[no-]shallow-submodules]
-	  [--jobs <n>] [--] <repository> [<directory>]
+	  [--[no-]remote-submodules] [--jobs <n>] [--] <repository>
+	  [<directory>]
 
 DESCRIPTION
 -----------
@@ -260,6 +261,12 @@ or `--mirror` is given)
 --[no-]shallow-submodules::
 	All submodules which are cloned will be shallow with a depth of 1.
 
+--[no-]remote-submodules::
+	All submodules which are cloned will use the status of the submodule’s
+	remote-tracking branch to update the submodule, rather than the
+	superproject’s recorded SHA-1. Equivalent to passing `--remote` to
+	`git submodule update`.
+
 --separate-git-dir=<git dir>::
 	Instead of placing the cloned repository where it is supposed
 	to be, place the cloned repository at the specified directory,

builtin/clone.c

@@ -67,6 +67,7 @@ static int max_jobs = -1;
 static struct string_list option_recurse_submodules = STRING_LIST_INIT_NODUP;
 static struct list_objects_filter_options filter_options;
 static struct string_list server_options = STRING_LIST_INIT_NODUP;
+static int option_remote_submodules;
 
 static int recurse_submodules_cb(const struct option *opt,
 				 const char *arg, int unset)
@@ -142,6 +143,8 @@ static struct option builtin_clone_options[] = {
 	OPT_SET_INT('6', "ipv6", &family, N_("use IPv6 addresses only"),
 			TRANSPORT_FAMILY_IPV6),
 	OPT_PARSE_LIST_OBJECTS_FILTER(&filter_options),
+	OPT_BOOL(0, "remote-submodules", &option_remote_submodules,
+		    N_("any cloned submodules will use their remote-tracking branch")),
 	OPT_END()
 };
 
@@ -790,6 +793,11 @@ static int checkout(int submodule_progress)
 		if (option_verbosity < 0)
 			argv_array_push(&args, "--quiet");
 
+		if (option_remote_submodules) {
+			argv_array_push(&args, "--remote");
+			argv_array_push(&args, "--no-fetch");
+		}
+
 		err = run_command_v_opt(args.argv, RUN_GIT_CMD);
 		argv_array_clear(&args);
 	}

t/t5617-clone-submodules-remote.sh

@@ -0,0 +1,54 @@
+#!/bin/sh
+
+test_description='Test cloning repos with submodules using remote-tracking branches'
+
+. ./test-lib.sh
+
+pwd=$(pwd)
+
+test_expect_success 'setup' '
+	git checkout -b master &&
+	test_commit commit1 &&
+	mkdir sub &&
+	(
+		cd sub &&
+		git init &&
+		test_commit subcommit1 &&
+		git tag sub_when_added_to_super
+	) &&
+	git submodule add "file://$pwd/sub" sub &&
+	git commit -m "add submodule" &&
+	(
+		cd sub &&
+		test_commit subcommit2
+	)
+'
+
+test_expect_success 'clone with --no-remote-submodules' '
+	test_when_finished "rm -rf super_clone" &&
+	git clone --recurse-submodules --no-remote-submodules "file://$pwd/." super_clone &&
+	(
+		cd super_clone/sub &&
+		git diff --exit-code sub_when_added_to_super
+	)
+'
+
+test_expect_success 'clone with --remote-submodules' '
+	test_when_finished "rm -rf super_clone" &&
+	git clone --recurse-submodules --remote-submodules "file://$pwd/." super_clone &&
+	(
+		cd super_clone/sub &&
+		git diff --exit-code remotes/origin/master
+	)
+'
+
+test_expect_success 'check the default is --no-remote-submodules' '
+	test_when_finished "rm -rf super_clone" &&
+	git clone --recurse-submodules "file://$pwd/." super_clone &&
+	(
+		cd super_clone/sub &&
+		git diff --exit-code sub_when_added_to_super
+	)
+'
+
+test_done