[PATCH v2 1/2] t4255: test am submodule with diff.submodule

[Doug Kelly <dougk.ff7@gmail.com>]

git am will break when using diff.submodule=log; add some test cases
to illustrate this breakage as simply as possible.  There are
currently two ways this can fail:

* With errors ("unrecognized input"), if only change
* Silently (no submodule change), if other files change

Test for both conditions and ensure without diff.submodule this works.

Signed-off-by: Doug Kelly <dougk.ff7@gmail.com>
---
 t/t4255-am-submodule.sh | 84 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)

diff --git a/t/t4255-am-submodule.sh b/t/t4255-am-submodule.sh
index 8bde7db..a2dc083 100755
--- a/t/t4255-am-submodule.sh
+++ b/t/t4255-am-submodule.sh
@@ -18,4 +18,88 @@ am_3way () {
 KNOWN_FAILURE_NOFF_MERGE_ATTEMPTS_TO_MERGE_REMOVED_SUBMODULE_FILES=1
 test_submodule_switch "am_3way"
 
+test_expect_success 'setup diff.submodule' '
+	echo one >one &&
+	git add one &&
+	test_tick &&
+	git commit -m initial &&
+	INITIAL=$(git rev-parse HEAD) &&
+
+	git init submodule &&
+	(
+		cd submodule &&
+		echo two >two &&
+		git add two &&
+		test_tick &&
+		git commit -m "initial submodule" &&
+		git rev-parse HEAD >../initial-submodule
+	) &&
+	git submodule add ./submodule &&
+	test_tick &&
+	git commit -m first &&
+
+	(
+		cd submodule &&
+		echo three >three &&
+		git add three &&
+		test_tick &&
+		git commit -m "first submodule" &&
+		git rev-parse HEAD >../first-submodule
+	) &&
+	git add submodule &&
+	test_tick &&
+	git commit -m second &&
+	SECOND=$(git rev-parse HEAD) &&
+
+	(
+		cd submodule &&
+		git mv two four &&
+		test_tick &&
+		git commit -m "second submodule" &&
+		git rev-parse HEAD >../second-submodule
+	) &&
+	git add submodule &&
+	echo four >four &&
+	git add four &&
+	test_tick &&
+	git commit -m third &&
+	THIRD=$(git rev-parse HEAD) &&
+	git submodule update --init
+'
+
+run_test() {
+	START_COMMIT=$1 &&
+	EXPECT=$2 &&
+	(git am --abort || true) &&
+	git reset --hard $START_COMMIT &&
+	rm -f *.patch &&
+	git format-patch -1 &&
+	git reset --hard $START_COMMIT^ &&
+	git submodule update &&
+	git am *.patch &&
+	git submodule update &&
+	(cd submodule && git rev-parse HEAD >../actual) &&
+	test_cmp $EXPECT actual
+}
+
+test_expect_success 'diff.submodule unset' '
+	(git config --unset diff.submodule || true) &&
+	run_test $SECOND first-submodule
+'
+
+test_expect_success 'diff.submodule unset with extra file' '
+	(git config --unset diff.submodule || true) &&
+	run_test $THIRD second-submodule
+'
+
+test_expect_failure 'diff.submodule=log' '
+	git config diff.submodule log &&
+	run_test $SECOND first-submodule
+'
+
+test_expect_failure 'diff.submodule=log with extra file' '
+	git config diff.submodule log &&
+	run_test $THIRD second-submodule
+'
+
 test_done
-- 
2.0.5