t/t5324-split-commit-graph.sh

   1 #!/bin/sh
   2
   3 test_description='split commit graph'
   4 . ./test-lib.sh
   5
   6 GIT_TEST_COMMIT_GRAPH=0
   7 GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=0
   8
   9 test_expect_success 'setup repo' '
  10         git init &&
  11         git config core.commitGraph true &&
  12         git config gc.writeCommitGraph false &&
  13         infodir=".git/objects/info" &&
  14         graphdir="$infodir/commit-graphs" &&
  15         test_oid_cache <<-EOM
  16         shallow sha1:2132
  17         shallow sha256:2436
  18
  19         base sha1:1408
  20         base sha256:1528
  21
  22         oid_version sha1:1
  23         oid_version sha256:2
  24         EOM
  25 '
  26
  27 graph_read_expect() {
  28         NUM_BASE=0
  29         if test ! -z $2
  30         then
  31                 NUM_BASE=$2
  32         fi
  33         cat >expect <<- EOF
  34         header: 43475048 1 $(test_oid oid_version) 4 $NUM_BASE
  35         num_commits: $1
  36         chunks: oid_fanout oid_lookup commit_metadata generation_data
  37         EOF
  38         test-tool read-graph >output &&
  39         test_cmp expect output
  40 }
  41
  42 test_expect_success POSIXPERM 'tweak umask for modebit tests' '
  43         umask 022
  44 '
  45
  46 test_expect_success 'create commits and write commit-graph' '
  47         for i in $(test_seq 3)
  48         do
  49                 test_commit $i &&
  50                 git branch commits/$i || return 1
  51         done &&
  52         git commit-graph write --reachable &&
  53         test_path_is_file $infodir/commit-graph &&
  54         graph_read_expect 3
  55 '
  56
  57 graph_git_two_modes() {
  58         git -c core.commitGraph=true $1 >output
  59         git -c core.commitGraph=false $1 >expect
  60         test_cmp expect output
  61 }
  62
  63 graph_git_behavior() {
  64         MSG=$1
  65         BRANCH=$2
  66         COMPARE=$3
  67         test_expect_success "check normal git operations: $MSG" '
  68                 graph_git_two_modes "log --oneline $BRANCH" &&
  69                 graph_git_two_modes "log --topo-order $BRANCH" &&
  70                 graph_git_two_modes "log --graph $COMPARE..$BRANCH" &&
  71                 graph_git_two_modes "branch -vv" &&
  72                 graph_git_two_modes "merge-base -a $BRANCH $COMPARE"
  73         '
  74 }
  75
  76 graph_git_behavior 'graph exists' commits/3 commits/1
  77
  78 verify_chain_files_exist() {
  79         for hash in $(cat $1/commit-graph-chain)
  80         do
  81                 test_path_is_file $1/graph-$hash.graph || return 1
  82         done
  83 }
  84
  85 test_expect_success 'add more commits, and write a new base graph' '
  86         git reset --hard commits/1 &&
  87         for i in $(test_seq 4 5)
  88         do
  89                 test_commit $i &&
  90                 git branch commits/$i || return 1
  91         done &&
  92         git reset --hard commits/2 &&
  93         for i in $(test_seq 6 10)
  94         do
  95                 test_commit $i &&
  96                 git branch commits/$i || return 1
  97         done &&
  98         git reset --hard commits/2 &&
  99         git merge commits/4 &&
 100         git branch merge/1 &&
 101         git reset --hard commits/4 &&
 102         git merge commits/6 &&
 103         git branch merge/2 &&
 104         git commit-graph write --reachable &&
 105         graph_read_expect 12
 106 '
 107
 108 test_expect_success 'fork and fail to base a chain on a commit-graph file' '
 109         test_when_finished rm -rf fork &&
 110         git clone . fork &&
 111         (
 112                 cd fork &&
 113                 rm .git/objects/info/commit-graph &&
 114                 echo "$(pwd)/../.git/objects" >.git/objects/info/alternates &&
 115                 test_commit new-commit &&
 116                 git commit-graph write --reachable --split &&
 117                 test_path_is_file $graphdir/commit-graph-chain &&
 118                 test_line_count = 1 $graphdir/commit-graph-chain &&
 119                 verify_chain_files_exist $graphdir
 120         )
 121 '
 122
 123 test_expect_success 'add three more commits, write a tip graph' '
 124         git reset --hard commits/3 &&
 125         git merge merge/1 &&
 126         git merge commits/5 &&
 127         git merge merge/2 &&
 128         git branch merge/3 &&
 129         git commit-graph write --reachable --split &&
 130         test_path_is_missing $infodir/commit-graph &&
 131         test_path_is_file $graphdir/commit-graph-chain &&
 132         ls $graphdir/graph-*.graph >graph-files &&
 133         test_line_count = 2 graph-files &&
 134         verify_chain_files_exist $graphdir
 135 '
 136
 137 graph_git_behavior 'split commit-graph: merge 3 vs 2' merge/3 merge/2
 138
 139 test_expect_success 'add one commit, write a tip graph' '
 140         test_commit 11 &&
 141         git branch commits/11 &&
 142         git commit-graph write --reachable --split &&
 143         test_path_is_missing $infodir/commit-graph &&
 144         test_path_is_file $graphdir/commit-graph-chain &&
 145         ls $graphdir/graph-*.graph >graph-files &&
 146         test_line_count = 3 graph-files &&
 147         verify_chain_files_exist $graphdir
 148 '
 149
 150 graph_git_behavior 'three-layer commit-graph: commit 11 vs 6' commits/11 commits/6
 151
 152 test_expect_success 'add one commit, write a merged graph' '
 153         test_commit 12 &&
 154         git branch commits/12 &&
 155         git commit-graph write --reachable --split &&
 156         test_path_is_file $graphdir/commit-graph-chain &&
 157         test_line_count = 2 $graphdir/commit-graph-chain &&
 158         ls $graphdir/graph-*.graph >graph-files &&
 159         test_line_count = 2 graph-files &&
 160         verify_chain_files_exist $graphdir
 161 '
 162
 163 graph_git_behavior 'merged commit-graph: commit 12 vs 6' commits/12 commits/6
 164
 165 test_expect_success 'create fork and chain across alternate' '
 166         git clone . fork &&
 167         (
 168                 cd fork &&
 169                 git config core.commitGraph true &&
 170                 rm -rf $graphdir &&
 171                 echo "$(pwd)/../.git/objects" >.git/objects/info/alternates &&
 172                 test_commit 13 &&
 173                 git branch commits/13 &&
 174                 git commit-graph write --reachable --split &&
 175                 test_path_is_file $graphdir/commit-graph-chain &&
 176                 test_line_count = 3 $graphdir/commit-graph-chain &&
 177                 ls $graphdir/graph-*.graph >graph-files &&
 178                 test_line_count = 1 graph-files &&
 179                 git -c core.commitGraph=true  rev-list HEAD >expect &&
 180                 git -c core.commitGraph=false rev-list HEAD >actual &&
 181                 test_cmp expect actual &&
 182                 test_commit 14 &&
 183                 git commit-graph write --reachable --split --object-dir=.git/objects/ &&
 184                 test_line_count = 3 $graphdir/commit-graph-chain &&
 185                 ls $graphdir/graph-*.graph >graph-files &&
 186                 test_line_count = 1 graph-files
 187         )
 188 '
 189
 190 graph_git_behavior 'alternate: commit 13 vs 6' commits/13 commits/6
 191
 192 test_expect_success 'test merge stragety constants' '
 193         git clone . merge-2 &&
 194         (
 195                 cd merge-2 &&
 196                 git config core.commitGraph true &&
 197                 test_line_count = 2 $graphdir/commit-graph-chain &&
 198                 test_commit 14 &&
 199                 git commit-graph write --reachable --split --size-multiple=2 &&
 200                 test_line_count = 3 $graphdir/commit-graph-chain
 201
 202         ) &&
 203         git clone . merge-10 &&
 204         (
 205                 cd merge-10 &&
 206                 git config core.commitGraph true &&
 207                 test_line_count = 2 $graphdir/commit-graph-chain &&
 208                 test_commit 14 &&
 209                 git commit-graph write --reachable --split --size-multiple=10 &&
 210                 test_line_count = 1 $graphdir/commit-graph-chain &&
 211                 ls $graphdir/graph-*.graph >graph-files &&
 212                 test_line_count = 1 graph-files
 213         ) &&
 214         git clone . merge-10-expire &&
 215         (
 216                 cd merge-10-expire &&
 217                 git config core.commitGraph true &&
 218                 test_line_count = 2 $graphdir/commit-graph-chain &&
 219                 test_commit 15 &&
 220                 touch $graphdir/to-delete.graph $graphdir/to-keep.graph &&
 221                 test-tool chmtime =1546362000 $graphdir/to-delete.graph &&
 222                 test-tool chmtime =1546362001 $graphdir/to-keep.graph &&
 223                 git commit-graph write --reachable --split --size-multiple=10 \
 224                         --expire-time="2019-01-01 12:00 -05:00" &&
 225                 test_line_count = 1 $graphdir/commit-graph-chain &&
 226                 test_path_is_missing $graphdir/to-delete.graph &&
 227                 test_path_is_file $graphdir/to-keep.graph &&
 228                 ls $graphdir/graph-*.graph >graph-files &&
 229                 test_line_count = 3 graph-files
 230         ) &&
 231         git clone --no-hardlinks . max-commits &&
 232         (
 233                 cd max-commits &&
 234                 git config core.commitGraph true &&
 235                 test_line_count = 2 $graphdir/commit-graph-chain &&
 236                 test_commit 16 &&
 237                 test_commit 17 &&
 238                 git commit-graph write --reachable --split --max-commits=1 &&
 239                 test_line_count = 1 $graphdir/commit-graph-chain &&
 240                 ls $graphdir/graph-*.graph >graph-files &&
 241                 test_line_count = 1 graph-files
 242         )
 243 '
 244
 245 test_expect_success 'remove commit-graph-chain file after flattening' '
 246         git clone . flatten &&
 247         (
 248                 cd flatten &&
 249                 test_line_count = 2 $graphdir/commit-graph-chain &&
 250                 git commit-graph write --reachable &&
 251                 test_path_is_missing $graphdir/commit-graph-chain &&
 252                 ls $graphdir >graph-files &&
 253                 test_line_count = 0 graph-files
 254         )
 255 '
 256
 257 corrupt_file() {
 258         file=$1
 259         pos=$2
 260         data="${3:-\0}"
 261         chmod a+w "$file" &&
 262         printf "$data" | dd of="$file" bs=1 seek="$pos" conv=notrunc
 263 }
 264
 265 test_expect_success 'verify hashes along chain, even in shallow' '
 266         git clone --no-hardlinks . verify &&
 267         (
 268                 cd verify &&
 269                 git commit-graph verify &&
 270                 base_file=$graphdir/graph-$(head -n 1 $graphdir/commit-graph-chain).graph &&
 271                 corrupt_file "$base_file" $(test_oid shallow) "\01" &&
 272                 test_must_fail git commit-graph verify --shallow 2>test_err &&
 273                 grep -v "^+" test_err >err &&
 274                 test_i18ngrep "incorrect checksum" err
 275         )
 276 '
 277
 278 test_expect_success 'verify --shallow does not check base contents' '
 279         git clone --no-hardlinks . verify-shallow &&
 280         (
 281                 cd verify-shallow &&
 282                 git commit-graph verify &&
 283                 base_file=$graphdir/graph-$(head -n 1 $graphdir/commit-graph-chain).graph &&
 284                 corrupt_file "$base_file" 1000 "\01" &&
 285                 git commit-graph verify --shallow &&
 286                 test_must_fail git commit-graph verify 2>test_err &&
 287                 grep -v "^+" test_err >err &&
 288                 test_i18ngrep "incorrect checksum" err
 289         )
 290 '
 291
 292 test_expect_success 'warn on base graph chunk incorrect' '
 293         git clone --no-hardlinks . base-chunk &&
 294         (
 295                 cd base-chunk &&
 296                 git commit-graph verify &&
 297                 base_file=$graphdir/graph-$(tail -n 1 $graphdir/commit-graph-chain).graph &&
 298                 corrupt_file "$base_file" $(test_oid base) "\01" &&
 299                 git commit-graph verify --shallow 2>test_err &&
 300                 grep -v "^+" test_err >err &&
 301                 test_i18ngrep "commit-graph chain does not match" err
 302         )
 303 '
 304
 305 test_expect_success 'verify after commit-graph-chain corruption' '
 306         git clone --no-hardlinks . verify-chain &&
 307         (
 308                 cd verify-chain &&
 309                 corrupt_file "$graphdir/commit-graph-chain" 60 "G" &&
 310                 git commit-graph verify 2>test_err &&
 311                 grep -v "^+" test_err >err &&
 312                 test_i18ngrep "invalid commit-graph chain" err &&
 313                 corrupt_file "$graphdir/commit-graph-chain" 60 "A" &&
 314                 git commit-graph verify 2>test_err &&
 315                 grep -v "^+" test_err >err &&
 316                 test_i18ngrep "unable to find all commit-graph files" err
 317         )
 318 '
 319
 320 test_expect_success 'verify across alternates' '
 321         git clone --no-hardlinks . verify-alt &&
 322         (
 323                 cd verify-alt &&
 324                 rm -rf $graphdir &&
 325                 altdir="$(pwd)/../.git/objects" &&
 326                 echo "$altdir" >.git/objects/info/alternates &&
 327                 git commit-graph verify --object-dir="$altdir/" &&
 328                 test_commit extra &&
 329                 git commit-graph write --reachable --split &&
 330                 tip_file=$graphdir/graph-$(tail -n 1 $graphdir/commit-graph-chain).graph &&
 331                 corrupt_file "$tip_file" 100 "\01" &&
 332                 test_must_fail git commit-graph verify --shallow 2>test_err &&
 333                 grep -v "^+" test_err >err &&
 334                 test_i18ngrep "commit-graph has incorrect fanout value" err
 335         )
 336 '
 337
 338 test_expect_success 'add octopus merge' '
 339         git reset --hard commits/10 &&
 340         git merge commits/3 commits/4 &&
 341         git branch merge/octopus &&
 342         git commit-graph write --reachable --split &&
 343         git commit-graph verify --progress 2>err &&
 344         test_line_count = 3 err &&
 345         test_i18ngrep ! warning err &&
 346         test_line_count = 3 $graphdir/commit-graph-chain
 347 '
 348
 349 graph_git_behavior 'graph exists' merge/octopus commits/12
 350
 351 test_expect_success 'split across alternate where alternate is not split' '
 352         git commit-graph write --reachable &&
 353         test_path_is_file .git/objects/info/commit-graph &&
 354         cp .git/objects/info/commit-graph . &&
 355         git clone --no-hardlinks . alt-split &&
 356         (
 357                 cd alt-split &&
 358                 rm -f .git/objects/info/commit-graph &&
 359                 echo "$(pwd)"/../.git/objects >.git/objects/info/alternates &&
 360                 test_commit 18 &&
 361                 git commit-graph write --reachable --split &&
 362                 test_line_count = 1 $graphdir/commit-graph-chain
 363         ) &&
 364         test_cmp commit-graph .git/objects/info/commit-graph
 365 '
 366
 367 test_expect_success '--split=no-merge always writes an incremental' '
 368         test_when_finished rm -rf a b &&
 369         rm -rf $graphdir $infodir/commit-graph &&
 370         git reset --hard commits/2 &&
 371         git rev-list HEAD~1 >a &&
 372         git rev-list HEAD >b &&
 373         git commit-graph write --split --stdin-commits <a &&
 374         git commit-graph write --split=no-merge --stdin-commits <b &&
 375         test_line_count = 2 $graphdir/commit-graph-chain
 376 '
 377
 378 test_expect_success '--split=replace replaces the chain' '
 379         rm -rf $graphdir $infodir/commit-graph &&
 380         git reset --hard commits/3 &&
 381         git rev-list -1 HEAD~2 >a &&
 382         git rev-list -1 HEAD~1 >b &&
 383         git rev-list -1 HEAD >c &&
 384         git commit-graph write --split=no-merge --stdin-commits <a &&
 385         git commit-graph write --split=no-merge --stdin-commits <b &&
 386         git commit-graph write --split=no-merge --stdin-commits <c &&
 387         test_line_count = 3 $graphdir/commit-graph-chain &&
 388         git commit-graph write --stdin-commits --split=replace <b &&
 389         test_path_is_missing $infodir/commit-graph &&
 390         test_path_is_file $graphdir/commit-graph-chain &&
 391         ls $graphdir/graph-*.graph >graph-files &&
 392         test_line_count = 1 graph-files &&
 393         verify_chain_files_exist $graphdir &&
 394         graph_read_expect 2
 395 '
 396
 397 test_expect_success ULIMIT_FILE_DESCRIPTORS 'handles file descriptor exhaustion' '
 398         git init ulimit &&
 399         (
 400                 cd ulimit &&
 401                 for i in $(test_seq 64)
 402                 do
 403                         test_commit $i &&
 404                         run_with_limited_open_files test_might_fail git commit-graph write \
 405                                 --split=no-merge --reachable || return 1
 406                 done
 407         )
 408 '
 409
 410 while read mode modebits
 411 do
 412         test_expect_success POSIXPERM "split commit-graph respects core.sharedrepository $mode" '
 413                 rm -rf $graphdir $infodir/commit-graph &&
 414                 git reset --hard commits/1 &&
 415                 test_config core.sharedrepository "$mode" &&
 416                 git commit-graph write --split --reachable &&
 417                 ls $graphdir/graph-*.graph >graph-files &&
 418                 test_line_count = 1 graph-files &&
 419                 echo "$modebits" >expect &&
 420                 test_modebits $graphdir/graph-*.graph >actual &&
 421                 test_cmp expect actual &&
 422                 test_modebits $graphdir/commit-graph-chain >actual &&
 423                 test_cmp expect actual
 424         '
 425 done <<\EOF
 426 0666 -r--r--r--
 427 0600 -r--------
 428 EOF
 429
 430 test_expect_success '--split=replace with partial Bloom data' '
 431         rm -rf $graphdir $infodir/commit-graph &&
 432         git reset --hard commits/3 &&
 433         git rev-list -1 HEAD~2 >a &&
 434         git rev-list -1 HEAD~1 >b &&
 435         git commit-graph write --split=no-merge --stdin-commits --changed-paths <a &&
 436         git commit-graph write --split=no-merge --stdin-commits <b &&
 437         git commit-graph write --split=replace --stdin-commits --changed-paths <c &&
 438         ls $graphdir/graph-*.graph >graph-files &&
 439         test_line_count = 1 graph-files &&
 440         verify_chain_files_exist $graphdir
 441 '
 442
 443 test_expect_success 'prevent regression for duplicate commits across layers' '
 444         git init dup &&
 445         git -C dup commit --allow-empty -m one &&
 446         git -C dup -c core.commitGraph=false commit-graph write --split=no-merge --reachable 2>err &&
 447         test_i18ngrep "attempting to write a commit-graph" err &&
 448         git -C dup commit-graph write --split=no-merge --reachable &&
 449         git -C dup commit --allow-empty -m two &&
 450         git -C dup commit-graph write --split=no-merge --reachable &&
 451         git -C dup commit --allow-empty -m three &&
 452         git -C dup commit-graph write --split --reachable &&
 453         git -C dup commit-graph verify
 454 '
 455
 456 NUM_FIRST_LAYER_COMMITS=64
 457 NUM_SECOND_LAYER_COMMITS=16
 458 NUM_THIRD_LAYER_COMMITS=7
 459 NUM_FOURTH_LAYER_COMMITS=8
 460 NUM_FIFTH_LAYER_COMMITS=16
 461 SECOND_LAYER_SEQUENCE_START=$(($NUM_FIRST_LAYER_COMMITS + 1))
 462 SECOND_LAYER_SEQUENCE_END=$(($SECOND_LAYER_SEQUENCE_START + $NUM_SECOND_LAYER_COMMITS - 1))
 463 THIRD_LAYER_SEQUENCE_START=$(($SECOND_LAYER_SEQUENCE_END + 1))
 464 THIRD_LAYER_SEQUENCE_END=$(($THIRD_LAYER_SEQUENCE_START + $NUM_THIRD_LAYER_COMMITS - 1))
 465 FOURTH_LAYER_SEQUENCE_START=$(($THIRD_LAYER_SEQUENCE_END + 1))
 466 FOURTH_LAYER_SEQUENCE_END=$(($FOURTH_LAYER_SEQUENCE_START + $NUM_FOURTH_LAYER_COMMITS - 1))
 467 FIFTH_LAYER_SEQUENCE_START=$(($FOURTH_LAYER_SEQUENCE_END + 1))
 468 FIFTH_LAYER_SEQUENCE_END=$(($FIFTH_LAYER_SEQUENCE_START + $NUM_FIFTH_LAYER_COMMITS - 1))
 469
 470 # Current split graph chain:
 471 #
 472 #     16 commits (No GDAT)
 473 # ------------------------
 474 #     64 commits (GDAT)
 475 #
 476 test_expect_success 'setup repo for mixed generation commit-graph-chain' '
 477         graphdir=".git/objects/info/commit-graphs" &&
 478         test_oid_cache <<-EOF &&
 479         oid_version sha1:1
 480         oid_version sha256:2
 481         EOF
 482         git init mixed &&
 483         (
 484                 cd mixed &&
 485                 git config core.commitGraph true &&
 486                 git config gc.writeCommitGraph false &&
 487                 for i in $(test_seq $NUM_FIRST_LAYER_COMMITS)
 488                 do
 489                         test_commit $i &&
 490                         git branch commits/$i || return 1
 491                 done &&
 492                 git commit-graph write --reachable --split &&
 493                 graph_read_expect $NUM_FIRST_LAYER_COMMITS &&
 494                 test_line_count = 1 $graphdir/commit-graph-chain &&
 495                 for i in $(test_seq $SECOND_LAYER_SEQUENCE_START $SECOND_LAYER_SEQUENCE_END)
 496                 do
 497                         test_commit $i &&
 498                         git branch commits/$i || return 1
 499                 done &&
 500                 GIT_TEST_COMMIT_GRAPH_NO_GDAT=1 git commit-graph write --reachable --split=no-merge &&
 501                 test_line_count = 2 $graphdir/commit-graph-chain &&
 502                 test-tool read-graph >output &&
 503                 cat >expect <<-EOF &&
 504                 header: 43475048 1 $(test_oid oid_version) 4 1
 505                 num_commits: $NUM_SECOND_LAYER_COMMITS
 506                 chunks: oid_fanout oid_lookup commit_metadata
 507                 EOF
 508                 test_cmp expect output &&
 509                 git commit-graph verify &&
 510                 cat $graphdir/commit-graph-chain
 511         )
 512 '
 513
 514 # The new layer will be added without generation data chunk as it was not
 515 # present on the layer underneath it.
 516 #
 517 #      7 commits (No GDAT)
 518 # ------------------------
 519 #     16 commits (No GDAT)
 520 # ------------------------
 521 #     64 commits (GDAT)
 522 #
 523 test_expect_success 'do not write generation data chunk if not present on existing tip' '
 524         git clone mixed mixed-no-gdat &&
 525         (
 526                 cd mixed-no-gdat &&
 527                 for i in $(test_seq $THIRD_LAYER_SEQUENCE_START $THIRD_LAYER_SEQUENCE_END)
 528                 do
 529                         test_commit $i &&
 530                         git branch commits/$i || return 1
 531                 done &&
 532                 git commit-graph write --reachable --split=no-merge &&
 533                 test_line_count = 3 $graphdir/commit-graph-chain &&
 534                 test-tool read-graph >output &&
 535                 cat >expect <<-EOF &&
 536                 header: 43475048 1 $(test_oid oid_version) 4 2
 537                 num_commits: $NUM_THIRD_LAYER_COMMITS
 538                 chunks: oid_fanout oid_lookup commit_metadata
 539                 EOF
 540                 test_cmp expect output &&
 541                 git commit-graph verify
 542         )
 543 '
 544
 545 # Number of commits in each layer of the split-commit graph before merge:
 546 #
 547 #      8 commits (No GDAT)
 548 # ------------------------
 549 #      7 commits (No GDAT)
 550 # ------------------------
 551 #     16 commits (No GDAT)
 552 # ------------------------
 553 #     64 commits (GDAT)
 554 #
 555 # The top two layers are merged and do not have generation data chunk as layer below them does
 556 # not have generation data chunk.
 557 #
 558 #     15 commits (No GDAT)
 559 # ------------------------
 560 #     16 commits (No GDAT)
 561 # ------------------------
 562 #     64 commits (GDAT)
 563 #
 564 test_expect_success 'do not write generation data chunk if the topmost remaining layer does not have generation data chunk' '
 565         git clone mixed-no-gdat mixed-merge-no-gdat &&
 566         (
 567                 cd mixed-merge-no-gdat &&
 568                 for i in $(test_seq $FOURTH_LAYER_SEQUENCE_START $FOURTH_LAYER_SEQUENCE_END)
 569                 do
 570                         test_commit $i &&
 571                         git branch commits/$i || return 1
 572                 done &&
 573                 git commit-graph write --reachable --split --size-multiple 1 &&
 574                 test_line_count = 3 $graphdir/commit-graph-chain &&
 575                 test-tool read-graph >output &&
 576                 cat >expect <<-EOF &&
 577                 header: 43475048 1 $(test_oid oid_version) 4 2
 578                 num_commits: $(($NUM_THIRD_LAYER_COMMITS + $NUM_FOURTH_LAYER_COMMITS))
 579                 chunks: oid_fanout oid_lookup commit_metadata
 580                 EOF
 581                 test_cmp expect output &&
 582                 git commit-graph verify
 583         )
 584 '
 585
 586 # Number of commits in each layer of the split-commit graph before merge:
 587 #
 588 #     16 commits (No GDAT)
 589 # ------------------------
 590 #     15 commits (No GDAT)
 591 # ------------------------
 592 #     16 commits (No GDAT)
 593 # ------------------------
 594 #     64 commits (GDAT)
 595 #
 596 # The top three layers are merged and has generation data chunk as the topmost remaining layer
 597 # has generation data chunk.
 598 #
 599 #     47 commits (GDAT)
 600 # ------------------------
 601 #     64 commits (GDAT)
 602 #
 603 test_expect_success 'write generation data chunk if topmost remaining layer has generation data chunk' '
 604         git clone mixed-merge-no-gdat mixed-merge-gdat &&
 605         (
 606                 cd mixed-merge-gdat &&
 607                 for i in $(test_seq $FIFTH_LAYER_SEQUENCE_START $FIFTH_LAYER_SEQUENCE_END)
 608                 do
 609                         test_commit $i &&
 610                         git branch commits/$i || return 1
 611                 done &&
 612                 git commit-graph write --reachable --split --size-multiple 1 &&
 613                 test_line_count = 2 $graphdir/commit-graph-chain &&
 614                 test-tool read-graph >output &&
 615                 cat >expect <<-EOF &&
 616                 header: 43475048 1 $(test_oid oid_version) 5 1
 617                 num_commits: $(($NUM_SECOND_LAYER_COMMITS + $NUM_THIRD_LAYER_COMMITS + $NUM_FOURTH_LAYER_COMMITS + $NUM_FIFTH_LAYER_COMMITS))
 618                 chunks: oid_fanout oid_lookup commit_metadata generation_data
 619                 EOF
 620                 test_cmp expect output
 621         )
 622 '
 623
 624 test_expect_success 'write generation data chunk when commit-graph chain is replaced' '
 625         git clone mixed mixed-replace &&
 626         (
 627                 cd mixed-replace &&
 628                 git commit-graph write --reachable --split=replace &&
 629                 test_path_is_file $graphdir/commit-graph-chain &&
 630                 test_line_count = 1 $graphdir/commit-graph-chain &&
 631                 verify_chain_files_exist $graphdir &&
 632                 graph_read_expect $(($NUM_FIRST_LAYER_COMMITS + $NUM_SECOND_LAYER_COMMITS)) &&
 633                 git commit-graph verify
 634         )
 635 '
 636
 637 test_done