t1092: compare sparse-checkout to sparse-index

Add a new 'sparse-index' repo alongside the 'full-checkout' and
'sparse-checkout' repos in t1092-sparse-checkout-compatibility.sh. Also
add run_on_sparse and test_sparse_match helpers. These helpers will be
used when the sparse index is implemented.

Add the GIT_TEST_SPARSE_INDEX environment variable to enable the
sparse-index by default. This can be enabled across all tests, but that
will only affect cases where the sparse-checkout feature is enabled.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/README

@@ -439,6 +439,9 @@ and "sha256".
 GIT_TEST_WRITE_REV_INDEX=<boolean>, when true enables the
 'pack.writeReverseIndex' setting.
 
+GIT_TEST_SPARSE_INDEX=<boolean>, when true enables index writes to use the
+sparse-index format by default.
+
 Naming Tests
 ------------
 

t/t1092-sparse-checkout-compatibility.sh

@@ -7,6 +7,7 @@ test_description='compare full workdir to sparse workdir'
 test_expect_success 'setup' '
 	git init initial-repo &&
 	(
+		GIT_TEST_SPARSE_INDEX=0 &&
 		cd initial-repo &&
 		echo a >a &&
 		echo "after deep" >e &&
@@ -87,23 +88,32 @@ init_repos () {
 
 	cp -r initial-repo sparse-checkout &&
 	git -C sparse-checkout reset --hard &&
-	git -C sparse-checkout sparse-checkout init --cone &&
+
+	cp -r initial-repo sparse-index &&
+	git -C sparse-index reset --hard &&
 
 	# initialize sparse-checkout definitions
-	git -C sparse-checkout sparse-checkout set deep
+	git -C sparse-checkout sparse-checkout init --cone &&
+	git -C sparse-checkout sparse-checkout set deep &&
+	GIT_TEST_SPARSE_INDEX=1 git -C sparse-index sparse-checkout init --cone &&
+	GIT_TEST_SPARSE_INDEX=1 git -C sparse-index sparse-checkout set deep
 }
 
 run_on_sparse () {
 	(
 		cd sparse-checkout &&
-		"$@" >../sparse-checkout-out 2>../sparse-checkout-err
+		GIT_TEST_SPARSE_INDEX=0 "$@" >../sparse-checkout-out 2>../sparse-checkout-err
+	) &&
+	(
+		cd sparse-index &&
+		GIT_TEST_SPARSE_INDEX=1 "$@" >../sparse-index-out 2>../sparse-index-err
 	)
 }
 
 run_on_all () {
 	(
 		cd full-checkout &&
-		"$@" >../full-checkout-out 2>../full-checkout-err
+		GIT_TEST_SPARSE_INDEX=0 "$@" >../full-checkout-out 2>../full-checkout-err
 	) &&
 	run_on_sparse "$@"
 }
@@ -114,6 +124,12 @@ test_all_match () {
 	test_cmp full-checkout-err sparse-checkout-err
 }
 
+test_sparse_match () {
+	run_on_sparse "$@" &&
+	test_cmp sparse-checkout-out sparse-index-out &&
+	test_cmp sparse-checkout-err sparse-index-err
+}
+
 test_expect_success 'status with options' '
 	init_repos &&
 	test_all_match git status --porcelain=v2 &&