clone: do not let --depth imply --shallow-submodules

In v2.9.0, we prematurely flipped the default to force cloning
submodules shallowly, when the superproject is getting cloned
shallowly.  This is likely to fail when the upstream repositories
submodules are cloned from a repository that is not prepared to
serve histories that ends at a commit that is not at the tip of a
branch, and we know the world is not yet ready.

Use a safer default to clone the submodules fully, unless the user
tells us that she knows that the upstream repository of the
submodules are willing to cooperate with "--shallow-submodules"
option.

Noticed-by: Vadim Eisenberg <VADIME@il.ibm.com>
Helped-by: Jeff King <peff@peff.net>
Helped-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-clone.txt

@@ -192,9 +192,8 @@ objects from the source repository into a pack in the cloned repository.
 	Create a 'shallow' clone with a history truncated to the
 	specified number of revisions. Implies `--single-branch` unless
 	`--no-single-branch` is given to fetch the histories near the
-	tips of all branches. This implies `--shallow-submodules`. If
-	you want to have a shallow superproject clone, but full submodules,
-	also pass `--no-shallow-submodules`.
+	tips of all branches. If you want to clone submodules shallowly,
+	also pass `--shallow-submodules`.
 
 --[no-]single-branch::
 	Clone only the history leading to the tip of a single branch,

builtin/clone.c

@@ -40,7 +40,7 @@ static const char * const builtin_clone_usage[] = {
 
 static int option_no_checkout, option_bare, option_mirror, option_single_branch = -1;
 static int option_local = -1, option_no_hardlinks, option_shared, option_recursive;
-static int option_shallow_submodules = -1;
+static int option_shallow_submodules;
 static char *option_template, *option_depth;
 static char *option_origin = NULL;
 static char *option_branch = NULL;
@@ -730,8 +730,7 @@ static int checkout(void)
 		struct argv_array args = ARGV_ARRAY_INIT;
 		argv_array_pushl(&args, "submodule", "update", "--init", "--recursive", NULL);
 
-		if (option_shallow_submodules == 1
-		    || (option_shallow_submodules == -1 && option_depth))
+		if (option_shallow_submodules == 1)
 			argv_array_push(&args, "--depth=1");
 
 		if (max_jobs != -1)

t/t5614-clone-submodules.sh

@@ -37,7 +37,22 @@ test_expect_success 'nonshallow clone implies nonshallow submodule' '
 	)
 '
 
-test_expect_success 'shallow clone implies shallow submodule' '
+test_expect_success 'shallow clone with shallow submodule' '
+	test_when_finished "rm -rf super_clone" &&
+	git clone --recurse-submodules --depth 2 --shallow-submodules "file://$pwd/." super_clone &&
+	(
+		cd super_clone &&
+		git log --oneline >lines &&
+		test_line_count = 2 lines
+	) &&
+	(
+		cd super_clone/sub &&
+		git log --oneline >lines &&
+		test_line_count = 1 lines
+	)
+'
+
+test_expect_success 'shallow clone does not imply shallow submodule' '
 	test_when_finished "rm -rf super_clone" &&
 	git clone --recurse-submodules --depth 2 "file://$pwd/." super_clone &&
 	(
@@ -48,7 +63,7 @@ test_expect_success 'shallow clone implies shallow submodule' '
 	(
 		cd super_clone/sub &&
 		git log --oneline >lines &&
-		test_line_count = 1 lines
+		test_line_count = 3 lines
 	)
 '