Adding upstream version 1:2.39.2.upstream/1%2.39.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 651 insertions, 0 deletions

diff --git a/t/t5324-split-commit-graph.sh b/t/t5324-split-commit-graph.sh
new file mode 100755
index 0000000..669ddc6
--- /dev/null
+++ b/t/t5324-split-commit-graph.sh
@@ -0,0 +1,651 @@
+#!/bin/sh
+
+test_description='split commit graph'
+. ./test-lib.sh
+
+GIT_TEST_COMMIT_GRAPH=0
+GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=0
+
+test_expect_success 'setup repo' '
+	git init &&
+	git config core.commitGraph true &&
+	git config gc.writeCommitGraph false &&
+	infodir=".git/objects/info" &&
+	graphdir="$infodir/commit-graphs" &&
+	test_oid_cache <<-EOM
+	shallow sha1:2132
+	shallow sha256:2436
+
+	base sha1:1408
+	base sha256:1528
+
+	oid_version sha1:1
+	oid_version sha256:2
+	EOM
+'
+
+graph_read_expect() {
+	NUM_BASE=0
+	if test ! -z $2
+	then
+		NUM_BASE=$2
+	fi
+	OPTIONS=
+	if test -z "$3"
+	then
+		OPTIONS=" read_generation_data"
+	fi
+	cat >expect <<- EOF
+	header: 43475048 1 $(test_oid oid_version) 4 $NUM_BASE
+	num_commits: $1
+	chunks: oid_fanout oid_lookup commit_metadata generation_data
+	options:$OPTIONS
+	EOF
+	test-tool read-graph >output &&
+	test_cmp expect output
+}
+
+test_expect_success POSIXPERM 'tweak umask for modebit tests' '
+	umask 022
+'
+
+test_expect_success 'create commits and write commit-graph' '
+	for i in $(test_seq 3)
+	do
+		test_commit $i &&
+		git branch commits/$i || return 1
+	done &&
+	git commit-graph write --reachable &&
+	test_path_is_file $infodir/commit-graph &&
+	graph_read_expect 3
+'
+
+graph_git_two_modes() {
+	git ${2:+ -C "$2"} -c core.commitGraph=true $1 >output &&
+	git ${2:+ -C "$2"} -c core.commitGraph=false $1 >expect &&
+	test_cmp expect output
+}
+
+graph_git_behavior() {
+	MSG=$1
+	BRANCH=$2
+	COMPARE=$3
+	DIR=$4
+	test_expect_success "check normal git operations: $MSG" '
+		graph_git_two_modes "log --oneline $BRANCH" "$DIR" &&
+		graph_git_two_modes "log --topo-order $BRANCH" "$DIR" &&
+		graph_git_two_modes "log --graph $COMPARE..$BRANCH" "$DIR" &&
+		graph_git_two_modes "branch -vv" "$DIR" &&
+		graph_git_two_modes "merge-base -a $BRANCH $COMPARE" "$DIR"
+	'
+}
+
+graph_git_behavior 'graph exists' commits/3 commits/1
+
+verify_chain_files_exist() {
+	for hash in $(cat $1/commit-graph-chain)
+	do
+		test_path_is_file $1/graph-$hash.graph || return 1
+	done
+}
+
+test_expect_success 'add more commits, and write a new base graph' '
+	git reset --hard commits/1 &&
+	for i in $(test_seq 4 5)
+	do
+		test_commit $i &&
+		git branch commits/$i || return 1
+	done &&
+	git reset --hard commits/2 &&
+	for i in $(test_seq 6 10)
+	do
+		test_commit $i &&
+		git branch commits/$i || return 1
+	done &&
+	git reset --hard commits/2 &&
+	git merge commits/4 &&
+	git branch merge/1 &&
+	git reset --hard commits/4 &&
+	git merge commits/6 &&
+	git branch merge/2 &&
+	git commit-graph write --reachable &&
+	graph_read_expect 12
+'
+
+test_expect_success 'fork and fail to base a chain on a commit-graph file' '
+	test_when_finished rm -rf fork &&
+	git clone . fork &&
+	(
+		cd fork &&
+		rm .git/objects/info/commit-graph &&
+		echo "$(pwd)/../.git/objects" >.git/objects/info/alternates &&
+		test_commit new-commit &&
+		git commit-graph write --reachable --split &&
+		test_path_is_file $graphdir/commit-graph-chain &&
+		test_line_count = 1 $graphdir/commit-graph-chain &&
+		verify_chain_files_exist $graphdir
+	)
+'
+
+test_expect_success 'add three more commits, write a tip graph' '
+	git reset --hard commits/3 &&
+	git merge merge/1 &&
+	git merge commits/5 &&
+	git merge merge/2 &&
+	git branch merge/3 &&
+	git commit-graph write --reachable --split &&
+	test_path_is_missing $infodir/commit-graph &&
+	test_path_is_file $graphdir/commit-graph-chain &&
+	ls $graphdir/graph-*.graph >graph-files &&
+	test_line_count = 2 graph-files &&
+	verify_chain_files_exist $graphdir
+'
+
+graph_git_behavior 'split commit-graph: merge 3 vs 2' merge/3 merge/2
+
+test_expect_success 'add one commit, write a tip graph' '
+	test_commit 11 &&
+	git branch commits/11 &&
+	git commit-graph write --reachable --split &&
+	test_path_is_missing $infodir/commit-graph &&
+	test_path_is_file $graphdir/commit-graph-chain &&
+	ls $graphdir/graph-*.graph >graph-files &&
+	test_line_count = 3 graph-files &&
+	verify_chain_files_exist $graphdir
+'
+
+graph_git_behavior 'three-layer commit-graph: commit 11 vs 6' commits/11 commits/6
+
+test_expect_success 'add one commit, write a merged graph' '
+	test_commit 12 &&
+	git branch commits/12 &&
+	git commit-graph write --reachable --split &&
+	test_path_is_file $graphdir/commit-graph-chain &&
+	test_line_count = 2 $graphdir/commit-graph-chain &&
+	ls $graphdir/graph-*.graph >graph-files &&
+	test_line_count = 2 graph-files &&
+	verify_chain_files_exist $graphdir
+'
+
+graph_git_behavior 'merged commit-graph: commit 12 vs 6' commits/12 commits/6
+
+test_expect_success 'create fork and chain across alternate' '
+	git clone . fork &&
+	(
+		cd fork &&
+		git config core.commitGraph true &&
+		rm -rf $graphdir &&
+		echo "$(pwd)/../.git/objects" >.git/objects/info/alternates &&
+		test_commit 13 &&
+		git branch commits/13 &&
+		git commit-graph write --reachable --split &&
+		test_path_is_file $graphdir/commit-graph-chain &&
+		test_line_count = 3 $graphdir/commit-graph-chain &&
+		ls $graphdir/graph-*.graph >graph-files &&
+		test_line_count = 1 graph-files &&
+		git -c core.commitGraph=true  rev-list HEAD >expect &&
+		git -c core.commitGraph=false rev-list HEAD >actual &&
+		test_cmp expect actual &&
+		test_commit 14 &&
+		git commit-graph write --reachable --split --object-dir=.git/objects/ &&
+		test_line_count = 3 $graphdir/commit-graph-chain &&
+		ls $graphdir/graph-*.graph >graph-files &&
+		test_line_count = 1 graph-files
+	)
+'
+
+if test -d fork
+then
+	graph_git_behavior 'alternate: commit 13 vs 6' commits/13 origin/commits/6 "fork"
+fi
+
+test_expect_success 'test merge stragety constants' '
+	git clone . merge-2 &&
+	(
+		cd merge-2 &&
+		git config core.commitGraph true &&
+		test_line_count = 2 $graphdir/commit-graph-chain &&
+		test_commit 14 &&
+		git commit-graph write --reachable --split --size-multiple=2 &&
+		test_line_count = 3 $graphdir/commit-graph-chain
+
+	) &&
+	git clone . merge-10 &&
+	(
+		cd merge-10 &&
+		git config core.commitGraph true &&
+		test_line_count = 2 $graphdir/commit-graph-chain &&
+		test_commit 14 &&
+		git commit-graph write --reachable --split --size-multiple=10 &&
+		test_line_count = 1 $graphdir/commit-graph-chain &&
+		ls $graphdir/graph-*.graph >graph-files &&
+		test_line_count = 1 graph-files
+	) &&
+	git clone . merge-10-expire &&
+	(
+		cd merge-10-expire &&
+		git config core.commitGraph true &&
+		test_line_count = 2 $graphdir/commit-graph-chain &&
+		test_commit 15 &&
+		touch $graphdir/to-delete.graph $graphdir/to-keep.graph &&
+		test-tool chmtime =1546362000 $graphdir/to-delete.graph &&
+		test-tool chmtime =1546362001 $graphdir/to-keep.graph &&
+		git commit-graph write --reachable --split --size-multiple=10 \
+			--expire-time="2019-01-01 12:00 -05:00" &&
+		test_line_count = 1 $graphdir/commit-graph-chain &&
+		test_path_is_missing $graphdir/to-delete.graph &&
+		test_path_is_file $graphdir/to-keep.graph &&
+		ls $graphdir/graph-*.graph >graph-files &&
+		test_line_count = 3 graph-files
+	) &&
+	git clone --no-hardlinks . max-commits &&
+	(
+		cd max-commits &&
+		git config core.commitGraph true &&
+		test_line_count = 2 $graphdir/commit-graph-chain &&
+		test_commit 16 &&
+		test_commit 17 &&
+		git commit-graph write --reachable --split --max-commits=1 &&
+		test_line_count = 1 $graphdir/commit-graph-chain &&
+		ls $graphdir/graph-*.graph >graph-files &&
+		test_line_count = 1 graph-files
+	)
+'
+
+test_expect_success 'remove commit-graph-chain file after flattening' '
+	git clone . flatten &&
+	(
+		cd flatten &&
+		test_line_count = 2 $graphdir/commit-graph-chain &&
+		git commit-graph write --reachable &&
+		test_path_is_missing $graphdir/commit-graph-chain &&
+		ls $graphdir >graph-files &&
+		test_line_count = 0 graph-files
+	)
+'
+
+corrupt_file() {
+	file=$1
+	pos=$2
+	data="${3:-\0}"
+	chmod a+w "$file" &&
+	printf "$data" | dd of="$file" bs=1 seek="$pos" conv=notrunc
+}
+
+test_expect_success 'verify hashes along chain, even in shallow' '
+	git clone --no-hardlinks . verify &&
+	(
+		cd verify &&
+		git commit-graph verify &&
+		base_file=$graphdir/graph-$(head -n 1 $graphdir/commit-graph-chain).graph &&
+		corrupt_file "$base_file" $(test_oid shallow) "\01" &&
+		test_must_fail git commit-graph verify --shallow 2>test_err &&
+		grep -v "^+" test_err >err &&
+		test_i18ngrep "incorrect checksum" err
+	)
+'
+
+test_expect_success 'verify --shallow does not check base contents' '
+	git clone --no-hardlinks . verify-shallow &&
+	(
+		cd verify-shallow &&
+		git commit-graph verify &&
+		base_file=$graphdir/graph-$(head -n 1 $graphdir/commit-graph-chain).graph &&
+		corrupt_file "$base_file" 1000 "\01" &&
+		git commit-graph verify --shallow &&
+		test_must_fail git commit-graph verify 2>test_err &&
+		grep -v "^+" test_err >err &&
+		test_i18ngrep "incorrect checksum" err
+	)
+'
+
+test_expect_success 'warn on base graph chunk incorrect' '
+	git clone --no-hardlinks . base-chunk &&
+	(
+		cd base-chunk &&
+		git commit-graph verify &&
+		base_file=$graphdir/graph-$(tail -n 1 $graphdir/commit-graph-chain).graph &&
+		corrupt_file "$base_file" $(test_oid base) "\01" &&
+		git commit-graph verify --shallow 2>test_err &&
+		grep -v "^+" test_err >err &&
+		test_i18ngrep "commit-graph chain does not match" err
+	)
+'
+
+test_expect_success 'verify after commit-graph-chain corruption' '
+	git clone --no-hardlinks . verify-chain &&
+	(
+		cd verify-chain &&
+		corrupt_file "$graphdir/commit-graph-chain" 60 "G" &&
+		git commit-graph verify 2>test_err &&
+		grep -v "^+" test_err >err &&
+		test_i18ngrep "invalid commit-graph chain" err &&
+		corrupt_file "$graphdir/commit-graph-chain" 60 "A" &&
+		git commit-graph verify 2>test_err &&
+		grep -v "^+" test_err >err &&
+		test_i18ngrep "unable to find all commit-graph files" err
+	)
+'
+
+test_expect_success 'verify across alternates' '
+	git clone --no-hardlinks . verify-alt &&
+	(
+		cd verify-alt &&
+		rm -rf $graphdir &&
+		altdir="$(pwd)/../.git/objects" &&
+		echo "$altdir" >.git/objects/info/alternates &&
+		git commit-graph verify --object-dir="$altdir/" &&
+		test_commit extra &&
+		git commit-graph write --reachable --split &&
+		tip_file=$graphdir/graph-$(tail -n 1 $graphdir/commit-graph-chain).graph &&
+		corrupt_file "$tip_file" 100 "\01" &&
+		test_must_fail git commit-graph verify --shallow 2>test_err &&
+		grep -v "^+" test_err >err &&
+		test_i18ngrep "commit-graph has incorrect fanout value" err
+	)
+'
+
+test_expect_success 'add octopus merge' '
+	git reset --hard commits/10 &&
+	git merge commits/3 commits/4 &&
+	git branch merge/octopus &&
+	git commit-graph write --reachable --split &&
+	git commit-graph verify --progress 2>err &&
+	test_line_count = 3 err &&
+	test_i18ngrep ! warning err &&
+	test_line_count = 3 $graphdir/commit-graph-chain
+'
+
+graph_git_behavior 'graph exists' merge/octopus commits/12
+
+test_expect_success 'split across alternate where alternate is not split' '
+	git commit-graph write --reachable &&
+	test_path_is_file .git/objects/info/commit-graph &&
+	cp .git/objects/info/commit-graph . &&
+	git clone --no-hardlinks . alt-split &&
+	(
+		cd alt-split &&
+		rm -f .git/objects/info/commit-graph &&
+		echo "$(pwd)"/../.git/objects >.git/objects/info/alternates &&
+		test_commit 18 &&
+		git commit-graph write --reachable --split &&
+		test_line_count = 1 $graphdir/commit-graph-chain
+	) &&
+	test_cmp commit-graph .git/objects/info/commit-graph
+'
+
+test_expect_success '--split=no-merge always writes an incremental' '
+	test_when_finished rm -rf a b &&
+	rm -rf $graphdir $infodir/commit-graph &&
+	git reset --hard commits/2 &&
+	git rev-list HEAD~1 >a &&
+	git rev-list HEAD >b &&
+	git commit-graph write --split --stdin-commits <a &&
+	git commit-graph write --split=no-merge --stdin-commits <b &&
+	test_line_count = 2 $graphdir/commit-graph-chain
+'
+
+test_expect_success '--split=replace replaces the chain' '
+	rm -rf $graphdir $infodir/commit-graph &&
+	git reset --hard commits/3 &&
+	git rev-list -1 HEAD~2 >a &&
+	git rev-list -1 HEAD~1 >b &&
+	git rev-list -1 HEAD >c &&
+	git commit-graph write --split=no-merge --stdin-commits <a &&
+	git commit-graph write --split=no-merge --stdin-commits <b &&
+	git commit-graph write --split=no-merge --stdin-commits <c &&
+	test_line_count = 3 $graphdir/commit-graph-chain &&
+	git commit-graph write --stdin-commits --split=replace <b &&
+	test_path_is_missing $infodir/commit-graph &&
+	test_path_is_file $graphdir/commit-graph-chain &&
+	ls $graphdir/graph-*.graph >graph-files &&
+	test_line_count = 1 graph-files &&
+	verify_chain_files_exist $graphdir &&
+	graph_read_expect 2
+'
+
+test_expect_success ULIMIT_FILE_DESCRIPTORS 'handles file descriptor exhaustion' '
+	git init ulimit &&
+	(
+		cd ulimit &&
+		for i in $(test_seq 64)
+		do
+			test_commit $i &&
+			run_with_limited_open_files test_might_fail git commit-graph write \
+				--split=no-merge --reachable || return 1
+		done
+	)
+'
+
+while read mode modebits
+do
+	test_expect_success POSIXPERM "split commit-graph respects core.sharedrepository $mode" '
+		rm -rf $graphdir $infodir/commit-graph &&
+		git reset --hard commits/1 &&
+		test_config core.sharedrepository "$mode" &&
+		git commit-graph write --split --reachable &&
+		ls $graphdir/graph-*.graph >graph-files &&
+		test_line_count = 1 graph-files &&
+		echo "$modebits" >expect &&
+		test_modebits $graphdir/graph-*.graph >actual &&
+		test_cmp expect actual &&
+		test_modebits $graphdir/commit-graph-chain >actual &&
+		test_cmp expect actual
+	'
+done <<\EOF
+0666 -r--r--r--
+0600 -r--------
+EOF
+
+test_expect_success '--split=replace with partial Bloom data' '
+	rm -rf $graphdir $infodir/commit-graph &&
+	git reset --hard commits/3 &&
+	git rev-list -1 HEAD~2 >a &&
+	git rev-list -1 HEAD~1 >b &&
+	git commit-graph write --split=no-merge --stdin-commits --changed-paths <a &&
+	git commit-graph write --split=no-merge --stdin-commits <b &&
+	git commit-graph write --split=replace --stdin-commits --changed-paths <c &&
+	ls $graphdir/graph-*.graph >graph-files &&
+	test_line_count = 1 graph-files &&
+	verify_chain_files_exist $graphdir
+'
+
+test_expect_success 'prevent regression for duplicate commits across layers' '
+	git init dup &&
+	git -C dup commit --allow-empty -m one &&
+	git -C dup -c core.commitGraph=false commit-graph write --split=no-merge --reachable 2>err &&
+	test_i18ngrep "attempting to write a commit-graph" err &&
+	git -C dup commit-graph write --split=no-merge --reachable &&
+	git -C dup commit --allow-empty -m two &&
+	git -C dup commit-graph write --split=no-merge --reachable &&
+	git -C dup commit --allow-empty -m three &&
+	git -C dup commit-graph write --split --reachable &&
+	git -C dup commit-graph verify
+'
+
+NUM_FIRST_LAYER_COMMITS=64
+NUM_SECOND_LAYER_COMMITS=16
+NUM_THIRD_LAYER_COMMITS=7
+NUM_FOURTH_LAYER_COMMITS=8
+NUM_FIFTH_LAYER_COMMITS=16
+SECOND_LAYER_SEQUENCE_START=$(($NUM_FIRST_LAYER_COMMITS + 1))
+SECOND_LAYER_SEQUENCE_END=$(($SECOND_LAYER_SEQUENCE_START + $NUM_SECOND_LAYER_COMMITS - 1))
+THIRD_LAYER_SEQUENCE_START=$(($SECOND_LAYER_SEQUENCE_END + 1))
+THIRD_LAYER_SEQUENCE_END=$(($THIRD_LAYER_SEQUENCE_START + $NUM_THIRD_LAYER_COMMITS - 1))
+FOURTH_LAYER_SEQUENCE_START=$(($THIRD_LAYER_SEQUENCE_END + 1))
+FOURTH_LAYER_SEQUENCE_END=$(($FOURTH_LAYER_SEQUENCE_START + $NUM_FOURTH_LAYER_COMMITS - 1))
+FIFTH_LAYER_SEQUENCE_START=$(($FOURTH_LAYER_SEQUENCE_END + 1))
+FIFTH_LAYER_SEQUENCE_END=$(($FIFTH_LAYER_SEQUENCE_START + $NUM_FIFTH_LAYER_COMMITS - 1))
+
+# Current split graph chain:
+#
+#     16 commits (No GDAT)
+# ------------------------
+#     64 commits (GDAT)
+#
+test_expect_success 'setup repo for mixed generation commit-graph-chain' '
+	graphdir=".git/objects/info/commit-graphs" &&
+	test_oid_cache <<-EOF &&
+	oid_version sha1:1
+	oid_version sha256:2
+	EOF
+	git init mixed &&
+	(
+		cd mixed &&
+		git config core.commitGraph true &&
+		git config gc.writeCommitGraph false &&
+		for i in $(test_seq $NUM_FIRST_LAYER_COMMITS)
+		do
+			test_commit $i &&
+			git branch commits/$i || return 1
+		done &&
+		git -c commitGraph.generationVersion=2 commit-graph write --reachable --split &&
+		graph_read_expect $NUM_FIRST_LAYER_COMMITS &&
+		test_line_count = 1 $graphdir/commit-graph-chain &&
+		for i in $(test_seq $SECOND_LAYER_SEQUENCE_START $SECOND_LAYER_SEQUENCE_END)
+		do
+			test_commit $i &&
+			git branch commits/$i || return 1
+		done &&
+		git -c commitGraph.generationVersion=1 commit-graph write --reachable --split=no-merge &&
+		test_line_count = 2 $graphdir/commit-graph-chain &&
+		test-tool read-graph >output &&
+		cat >expect <<-EOF &&
+		header: 43475048 1 $(test_oid oid_version) 4 1
+		num_commits: $NUM_SECOND_LAYER_COMMITS
+		chunks: oid_fanout oid_lookup commit_metadata
+		options:
+		EOF
+		test_cmp expect output &&
+		git commit-graph verify &&
+		cat $graphdir/commit-graph-chain
+	)
+'
+
+# The new layer will be added without generation data chunk as it was not
+# present on the layer underneath it.
+#
+#      7 commits (No GDAT)
+# ------------------------
+#     16 commits (No GDAT)
+# ------------------------
+#     64 commits (GDAT)
+#
+test_expect_success 'do not write generation data chunk if not present on existing tip' '
+	git clone mixed mixed-no-gdat &&
+	(
+		cd mixed-no-gdat &&
+		for i in $(test_seq $THIRD_LAYER_SEQUENCE_START $THIRD_LAYER_SEQUENCE_END)
+		do
+			test_commit $i &&
+			git branch commits/$i || return 1
+		done &&
+		git commit-graph write --reachable --split=no-merge &&
+		test_line_count = 3 $graphdir/commit-graph-chain &&
+		test-tool read-graph >output &&
+		cat >expect <<-EOF &&
+		header: 43475048 1 $(test_oid oid_version) 4 2
+		num_commits: $NUM_THIRD_LAYER_COMMITS
+		chunks: oid_fanout oid_lookup commit_metadata
+		options:
+		EOF
+		test_cmp expect output &&
+		git commit-graph verify
+	)
+'
+
+# Number of commits in each layer of the split-commit graph before merge:
+#
+#      8 commits (No GDAT)
+# ------------------------
+#      7 commits (No GDAT)
+# ------------------------
+#     16 commits (No GDAT)
+# ------------------------
+#     64 commits (GDAT)
+#
+# The top two layers are merged and do not have generation data chunk as layer below them does
+# not have generation data chunk.
+#
+#     15 commits (No GDAT)
+# ------------------------
+#     16 commits (No GDAT)
+# ------------------------
+#     64 commits (GDAT)
+#
+test_expect_success 'do not write generation data chunk if the topmost remaining layer does not have generation data chunk' '
+	git clone mixed-no-gdat mixed-merge-no-gdat &&
+	(
+		cd mixed-merge-no-gdat &&
+		for i in $(test_seq $FOURTH_LAYER_SEQUENCE_START $FOURTH_LAYER_SEQUENCE_END)
+		do
+			test_commit $i &&
+			git branch commits/$i || return 1
+		done &&
+		git commit-graph write --reachable --split --size-multiple 1 &&
+		test_line_count = 3 $graphdir/commit-graph-chain &&
+		test-tool read-graph >output &&
+		cat >expect <<-EOF &&
+		header: 43475048 1 $(test_oid oid_version) 4 2
+		num_commits: $(($NUM_THIRD_LAYER_COMMITS + $NUM_FOURTH_LAYER_COMMITS))
+		chunks: oid_fanout oid_lookup commit_metadata
+		options:
+		EOF
+		test_cmp expect output &&
+		git commit-graph verify
+	)
+'
+
+# Number of commits in each layer of the split-commit graph before merge:
+#
+#     16 commits (No GDAT)
+# ------------------------
+#     15 commits (No GDAT)
+# ------------------------
+#     16 commits (No GDAT)
+# ------------------------
+#     64 commits (GDAT)
+#
+# The top three layers are merged and has generation data chunk as the topmost remaining layer
+# has generation data chunk.
+#
+#     47 commits (GDAT)
+# ------------------------
+#     64 commits (GDAT)
+#
+test_expect_success 'write generation data chunk if topmost remaining layer has generation data chunk' '
+	git clone mixed-merge-no-gdat mixed-merge-gdat &&
+	(
+		cd mixed-merge-gdat &&
+		for i in $(test_seq $FIFTH_LAYER_SEQUENCE_START $FIFTH_LAYER_SEQUENCE_END)
+		do
+			test_commit $i &&
+			git branch commits/$i || return 1
+		done &&
+		git commit-graph write --reachable --split --size-multiple 1 &&
+		test_line_count = 2 $graphdir/commit-graph-chain &&
+		test-tool read-graph >output &&
+		cat >expect <<-EOF &&
+		header: 43475048 1 $(test_oid oid_version) 5 1
+		num_commits: $(($NUM_SECOND_LAYER_COMMITS + $NUM_THIRD_LAYER_COMMITS + $NUM_FOURTH_LAYER_COMMITS + $NUM_FIFTH_LAYER_COMMITS))
+		chunks: oid_fanout oid_lookup commit_metadata generation_data
+		options: read_generation_data
+		EOF
+		test_cmp expect output
+	)
+'
+
+test_expect_success 'write generation data chunk when commit-graph chain is replaced' '
+	git clone mixed mixed-replace &&
+	(
+		cd mixed-replace &&
+		git commit-graph write --reachable --split=replace &&
+		test_path_is_file $graphdir/commit-graph-chain &&
+		test_line_count = 1 $graphdir/commit-graph-chain &&
+		verify_chain_files_exist $graphdir &&
+		graph_read_expect $(($NUM_FIRST_LAYER_COMMITS + $NUM_SECOND_LAYER_COMMITS)) &&
+		git commit-graph verify
+	)
+'
+
+test_done