[RFC PATCHv2 17/17] checkout: add config option to recurse into submodules by default

[Stefan Beller <sbeller@google.com>]

To make it easier for the user, who doesn't want to give the
`--recurse-submodules` option whenever they run checkout, have an
option for to set the default behavior for checkout to recurse into
submodules.

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 Documentation/config.txt       |  6 ++++++
 Documentation/git-checkout.txt |  5 +++--
 submodule.c                    |  6 +++---
 t/t2013-checkout-submodule.sh  | 16 ++++++++++++++++
 4 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index a0ab66aae7..67e0714358 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -949,6 +949,12 @@ clean.requireForce::
 	A boolean to make git-clean do nothing unless given -f,
 	-i or -n.   Defaults to true.
 
+checkout.recurseSubmodules::
+	This option can be set to a boolean value.
+	When set to true checkout will recurse into submodules and
+	update them. When set to false, which is the default, checkout
+	will leave submodules untouched.
+
 color.branch::
 	A boolean to enable/disable color in the output of
 	linkgit:git-branch[1]. May be set to `always`,
diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index a0ea2c5651..819c430b6e 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -260,8 +260,9 @@ section of linkgit:git-add[1] to learn how to operate the `--patch` mode.
 	Using --recurse-submodules will update the content of all initialized
 	submodules according to the commit recorded in the superproject. If
 	local modifications in a submodule would be overwritten the checkout
-	will fail until `-f` is used. If nothing (or --no-recurse-submodules)
-	is used, the work trees of submodules will not be updated.
+	will fail until `-f` is used. If `--no-recurse-submodules` is used,
+	the work trees of submodules will not be updated. If no command line
+	argument is given, `checkout.recurseSubmodules` is used as a default.
 
 <branch>::
 	Branch to checkout; if it refers to a branch (i.e., a name that,
diff --git a/submodule.c b/submodule.c
index 4253f7f044..e4e326bce4 100644
--- a/submodule.c
+++ b/submodule.c
@@ -160,10 +160,10 @@ int submodule_config(const char *var, const char *value, void *cb)
 		return 0;
 	} else if (starts_with(var, "submodule."))
 		return parse_submodule_config_option(var, value);
-	else if (!strcmp(var, "fetch.recursesubmodules")) {
+	else if (!strcmp(var, "fetch.recursesubmodules"))
 		config_fetch_recurse_submodules = parse_fetch_recurse_submodules_arg(var, value);
-		return 0;
-	}
+	else if (!strcmp(var, "checkout.recursesubmodules"))
+		config_update_recurse_submodules = parse_update_recurse_submodules_arg(var, value);
 	return 0;
 }
 
diff --git a/t/t2013-checkout-submodule.sh b/t/t2013-checkout-submodule.sh
index 33fb2f5de3..673021fb80 100755
--- a/t/t2013-checkout-submodule.sh
+++ b/t/t2013-checkout-submodule.sh
@@ -137,6 +137,22 @@ test_expect_success '"checkout --recurse-submodules" repopulates submodule' '
 	submodule_creation_must_succeed delete_submodule base
 '
 
+test_expect_success 'option checkout.recurseSubmodules updates submodule' '
+	test_config checkout.recurseSubmodules 1 &&
+	git checkout base &&
+	git checkout -b advanced-base &&
+	git -C submodule commit --allow-empty -m "empty commit" &&
+	git add submodule &&
+	git commit -m "advance submodule" &&
+	git checkout base &&
+	git diff-files --quiet &&
+	git diff-index --quiet --cached base &&
+	git checkout advanced-base &&
+	git diff-files --quiet &&
+	git diff-index --quiet --cached advanced-base &&
+	git checkout --recurse-submodules base
+'
+
 test_expect_success '"checkout --recurse-submodules" repopulates submodule in existing directory' '
 	git checkout --recurse-submodules delete_submodule &&
 	mkdir submodule &&
-- 
2.11.0.rc2.28.g2673dad