Merge branch 'sb/submodule-clone-rr'

"git clone --resurse-submodules --reference $path $URL" is a way to
reduce network transfer cost by borrowing objects in an existing
$path repository when cloning the superproject from $URL; it
learned to also peek into $path for presense of corresponding
repositories of submodules and borrow objects from there when able.

* sb/submodule-clone-rr:
  clone: recursive and reference option triggers submodule alternates
  clone: implement optional references
  clone: clarify option_reference as required
  clone: factor out checking for an alternate path
  submodule--helper update-clone: allow multiple references
  submodule--helper module-clone: allow multiple references
  t7408: merge short tests, factor out testing method
  t7408: modernize style

1 files changed, 116 insertions, 69 deletions

diff --git a/t/t7408-submodule-reference.sh b/t/t7408-submodule-reference.sh
index eaea19b8f2..1c1e289ffd 100755
--- a/t/t7408-submodule-reference.sh
+++ b/t/t7408-submodule-reference.sh
@@ -8,74 +8,121 @@ test_description='test clone --reference'
 
 base_dir=$(pwd)
 
-U=$base_dir/UPLOAD_LOG
-
-test_expect_success 'preparing first repository' \
-'test_create_repo A && cd A &&
-echo first > file1 &&
-git add file1 &&
-git commit -m A-initial'
-
-cd "$base_dir"
-
-test_expect_success 'preparing second repository' \
-'git clone A B && cd B &&
-echo second > file2 &&
-git add file2 &&
-git commit -m B-addition &&
-git repack -a -d &&
-git prune'
-
-cd "$base_dir"
-
-test_expect_success 'preparing superproject' \
-'test_create_repo super && cd super &&
-echo file > file &&
-git add file &&
-git commit -m B-super-initial'
-
-cd "$base_dir"
-
-test_expect_success 'submodule add --reference' \
-'cd super && git submodule add --reference ../B "file://$base_dir/A" sub &&
-git commit -m B-super-added'
-
-cd "$base_dir"
-
-test_expect_success 'after add: existence of info/alternates' \
-'test_line_count = 1 super/.git/modules/sub/objects/info/alternates'
-
-cd "$base_dir"
-
-test_expect_success 'that reference gets used with add' \
-'cd super/sub &&
-echo "0 objects, 0 kilobytes" > expected &&
-git count-objects > current &&
-diff expected current'
-
-cd "$base_dir"
-
-test_expect_success 'cloning superproject' \
-'git clone super super-clone'
-
-cd "$base_dir"
-
-test_expect_success 'update with reference' \
-'cd super-clone && git submodule update --init --reference ../B'
-
-cd "$base_dir"
-
-test_expect_success 'after update: existence of info/alternates' \
-'test_line_count = 1 super-clone/.git/modules/sub/objects/info/alternates'
-
-cd "$base_dir"
-
-test_expect_success 'that reference gets used with update' \
-'cd super-clone/sub &&
-echo "0 objects, 0 kilobytes" > expected &&
-git count-objects > current &&
-diff expected current'
-
-cd "$base_dir"
+test_alternate_is_used () {
+	alternates_file="$1" &&
+	working_dir="$2" &&
+	test_line_count = 1 "$alternates_file" &&
+	echo "0 objects, 0 kilobytes" >expect &&
+	git -C "$working_dir" count-objects >actual &&
+	test_cmp expect actual
+}
+
+test_expect_success 'preparing first repository' '
+	test_create_repo A &&
+	(
+		cd A &&
+		echo first >file1 &&
+		git add file1 &&
+		git commit -m A-initial
+	)
+'
+
+test_expect_success 'preparing second repository' '
+	git clone A B &&
+	(
+		cd B &&
+		echo second >file2 &&
+		git add file2 &&
+		git commit -m B-addition &&
+		git repack -a -d &&
+		git prune
+	)
+'
+
+test_expect_success 'preparing superproject' '
+	test_create_repo super &&
+	(
+		cd super &&
+		echo file >file &&
+		git add file &&
+		git commit -m B-super-initial
+	)
+'
+
+test_expect_success 'submodule add --reference uses alternates' '
+	(
+		cd super &&
+		git submodule add --reference ../B "file://$base_dir/A" sub &&
+		git commit -m B-super-added &&
+		git repack -ad
+	) &&
+	test_alternate_is_used super/.git/modules/sub/objects/info/alternates super/sub
+'
+
+test_expect_success 'that reference gets used with add' '
+	(
+		cd super/sub &&
+		echo "0 objects, 0 kilobytes" >expected &&
+		git count-objects >current &&
+		diff expected current
+	)
+'
+
+# The tests up to this point, and repositories created by them
+# (A, B, super and super/sub), are about setting up the stage
+# for subsequent tests and meant to be kept throughout the
+# remainder of the test.
+# Tests from here on, if they create their own test repository,
+# are expected to clean after themselves.
+
+test_expect_success 'updating superproject keeps alternates' '
+	test_when_finished "rm -rf super-clone" &&
+	git clone super super-clone &&
+	git -C super-clone submodule update --init --reference ../B &&
+	test_alternate_is_used super-clone/.git/modules/sub/objects/info/alternates super-clone/sub
+'
+
+test_expect_success 'submodules use alternates when cloning a superproject' '
+	test_when_finished "rm -rf super-clone" &&
+	git clone --reference super --recursive super super-clone &&
+	(
+		cd super-clone &&
+		# test superproject has alternates setup correctly
+		test_alternate_is_used .git/objects/info/alternates . &&
+		# test submodule has correct setup
+		test_alternate_is_used .git/modules/sub/objects/info/alternates sub
+	)
+'
+
+test_expect_success 'missing submodule alternate fails clone and submodule update' '
+	test_when_finished "rm -rf super-clone" &&
+	git clone super super2 &&
+	test_must_fail git clone --recursive --reference super2 super2 super-clone &&
+	(
+		cd super-clone &&
+		# test superproject has alternates setup correctly
+		test_alternate_is_used .git/objects/info/alternates . &&
+		# update of the submodule succeeds
+		test_must_fail git submodule update --init &&
+		# and we have no alternates:
+		test_must_fail test_alternate_is_used .git/modules/sub/objects/info/alternates sub &&
+		test_must_fail test_path_is_file sub/file1
+	)
+'
+
+test_expect_success 'ignoring missing submodule alternates passes clone and submodule update' '
+	test_when_finished "rm -rf super-clone" &&
+	git clone --reference-if-able super2 --recursive super2 super-clone &&
+	(
+		cd super-clone &&
+		# test superproject has alternates setup correctly
+		test_alternate_is_used .git/objects/info/alternates . &&
+		# update of the submodule succeeds
+		git submodule update --init &&
+		# and we have no alternates:
+		test_must_fail test_alternate_is_used .git/modules/sub/objects/info/alternates sub &&
+		test_path_is_file sub/file1
+	)
+'
 
 test_done