[PATCH 12/12] t0612: add tests to exercise Git/JGit reftable compatibility

From: Patrick Steinhardt <ps@pks.im>
Date: Apr 4, 2024, 13:25 UTC
Message-ID: <db66dd4155d80b714719e80ff90f64c1d36b97d0.1712235356.git.ps@pks.im>
In-Reply-To: <cover.1712235356.git.ps@pks.im>

While the reftable format is a recent introduction in Git, JGit already knows to read and write reftables since 2017. Given the complexity of the format there is a very real risk of incompatibilities between those two implementations, which is something that we really want to avoid.

Add some basic tests that verify that reftables written by Git and JGit can be read by the respective other implementation. For now this test suite is rather small, only covering basic functionality. But it serves as a good starting point and can be extended over time.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 t/t0612-reftable-jgit-compatibility.sh | 115 +++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100755 t/t0612-reftable-jgit-compatibility.sh

diff --git a/t/t0612-reftable-jgit-compatibility.sh b/t/t0612-reftable-jgit-compatibility.sh
new file mode 100755
index 0000000000..f25ea880a0
--- /dev/null
+++ b/t/t0612-reftable-jgit-compatibility.sh
@@ -0,0 +1,115 @@
+#!/bin/sh
+
+test_description='reftables are compatible with JGit'
+
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+GIT_TEST_DEFAULT_REF_FORMAT=reftable
+export GIT_TEST_DEFAULT_REF_FORMAT
+
+# JGit does not support the 'link' DIRC extension.
+GIT_TEST_SPLIT_INDEX=0
+export GIT_TEST_SPLIT_INDEX
+
+. ./test-lib.sh
+
+if ! test_have_prereq JGIT
+then
+	skip_all='skipping reftable JGit tests'
+	test_done
+fi
+
+if ! test_have_prereq SHA1
+then
+	skip_all='skipping reftable JGit tests; JGit does not support SHA256 reftables'
+	test_done
+fi
+
+test_commit_jgit () {
+	touch "$1" &&
+	jgit add "$1" &&
+	jgit commit -m "$1"
+}
+
+test_same_refs () {
+	git show-ref --head >cgit.actual &&
+	jgit show-ref >jgit-tabs.actual &&
+	tr "\t" " " <jgit-tabs.actual >jgit.actual &&
+	test_cmp cgit.actual jgit.actual
+}
+
+test_same_reflog () {
+	git reflog "$*" >cgit.actual &&
+	jgit reflog "$*" >jgit-newline.actual &&
+	sed '/^$/d' <jgit-newline.actual >jgit.actual &&
+	test_cmp cgit.actual jgit.actual
+}
+
+test_expect_success 'CGit repository can be read by JGit' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit A &&
+		test_same_refs &&
+		test_same_reflog HEAD
+	)
+'
+
+test_expect_success 'JGit repository can be read by CGit' '
+	test_when_finished "rm -rf repo" &&
+	# JGit does not provide a way to create a reftable-enabled repository.
+	git init repo &&
+	(
+		cd repo &&
+		touch file &&
+		jgit add file &&
+		jgit commit -m "initial commit" &&
+
+		test_same_refs &&
+		# Interestingly, JGit cannot read its own reflog here. CGit can
+		# though.
+		printf "%s HEAD@{0}: commit (initial): initial commit" "$(git rev-parse --short HEAD)" >expect &&
+		git reflog HEAD >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'mixed writes from JGit and CGit' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+
+		test_commit A &&
+		test_commit_jgit B &&
+		test_commit C &&
+		test_commit_jgit D &&
+
+		test_same_refs &&
+		test_same_reflog HEAD
+	)
+'
+
+test_expect_success 'JGit can read multi-level index' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+
+		test_commit A &&
+		awk "
+		    BEGIN {
+			print \"start\";
+			for (i = 0; i < 10000; i++)
+			    printf \"create refs/heads/branch-%d HEAD\n\", i;
+			print \"commit\";
+		    }
+		" >input &&
+		git update-ref --stdin <input &&
+
+		test_same_refs
+	)
+'
+
+test_done

-- 
2.44.GIT