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         OPTIONS=
  34         if test -z "$3"
  35         then
  36                 OPTIONS=" read_generation_data"
  37         fi
  38         cat >expect <<- EOF
  39         header: 43475048 1 $(test_oid oid_version) 4 $NUM_BASE
  40         num_commits: $1
  41         chunks: oid_fanout oid_lookup commit_metadata generation_data
  42         options:$OPTIONS
  43         EOF
  44         test-tool read-graph >output &&
  45         test_cmp expect output
  46 }
  47
  48 test_expect_success POSIXPERM 'tweak umask for modebit tests' '
  49         umask 022
  50 '
  51
  52 test_expect_success 'create commits and write commit-graph' '
  53         for i in $(test_seq 3)
  54         do
  55                 test_commit $i &&
  56                 git branch commits/$i || return 1
  57         done &&
  58         git commit-graph write --reachable &&
  59         test_path_is_file $infodir/commit-graph &&
  60         graph_read_expect 3
  61 '
  62
  63 graph_git_two_modes() {
  64         git ${2:+ -C "$2"} -c core.commitGraph=true $1 >output &&
  65         git ${2:+ -C "$2"} -c core.commitGraph=false $1 >expect &&
  66         test_cmp expect output
  67 }
  68
  69 graph_git_behavior() {
  70         MSG=$1
  71         BRANCH=$2
  72         COMPARE=$3
  73         DIR=$4
  74         test_expect_success "check normal git operations: $MSG" '
  75                 graph_git_two_modes "log --oneline $BRANCH" "$DIR" &&
  76                 graph_git_two_modes "log --topo-order $BRANCH" "$DIR" &&
  77                 graph_git_two_modes "log --graph $COMPARE..$BRANCH" "$DIR" &&
  78                 graph_git_two_modes "branch -vv" "$DIR" &&
  79                 graph_git_two_modes "merge-base -a $BRANCH $COMPARE" "$DIR"
  80         '
  81 }
  82
  83 graph_git_behavior 'graph exists' commits/3 commits/1
  84
  85 verify_chain_files_exist() {
  86         for hash in $(cat $1/commit-graph-chain)
  87         do
  88                 test_path_is_file $1/graph-$hash.graph || return 1
  89         done
  90 }
  91
  92 test_expect_success 'add more commits, and write a new base graph' '
  93         git reset --hard commits/1 &&
  94         for i in $(test_seq 4 5)
  95         do
  96                 test_commit $i &&
  97                 git branch commits/$i || return 1
  98         done &&
  99         git reset --hard commits/2 &&
 100         for i in $(test_seq 6 10)
 101         do
 102                 test_commit $i &&
 103                 git branch commits/$i || return 1
 104         done &&
 105         git reset --hard commits/2 &&
 106         git merge commits/4 &&
 107         git branch merge/1 &&
 108         git reset --hard commits/4 &&
 109         git merge commits/6 &&
 110         git branch merge/2 &&
 111         git commit-graph write --reachable &&
 112         graph_read_expect 12
 113 '
 114
 115 test_expect_success 'fork and fail to base a chain on a commit-graph file' '
 116         test_when_finished rm -rf fork &&
 117         git clone . fork &&
 118         (
 119                 cd fork &&
 120                 rm .git/objects/info/commit-graph &&
 121                 echo "$(pwd)/../.git/objects" >.git/objects/info/alternates &&
 122                 test_commit new-commit &&
 123                 git commit-graph write --reachable --split &&
 124                 test_path_is_file $graphdir/commit-graph-chain &&
 125                 test_line_count = 1 $graphdir/commit-graph-chain &&
 126                 verify_chain_files_exist $graphdir
 127         )
 128 '
 129
 130 test_expect_success 'add three more commits, write a tip graph' '
 131         git reset --hard commits/3 &&
 132         git merge merge/1 &&
 133         git merge commits/5 &&
 134         git merge merge/2 &&
 135         git branch merge/3 &&
 136         git commit-graph write --reachable --split &&
 137         test_path_is_missing $infodir/commit-graph &&
 138         test_path_is_file $graphdir/commit-graph-chain &&
 139         ls $graphdir/graph-*.graph >graph-files &&
 140         test_line_count = 2 graph-files &&
 141         verify_chain_files_exist $graphdir
 142 '
 143
 144 graph_git_behavior 'split commit-graph: merge 3 vs 2' merge/3 merge/2
 145
 146 test_expect_success 'add one commit, write a tip graph' '
 147         test_commit 11 &&
 148         git branch commits/11 &&
 149         git commit-graph write --reachable --split &&
 150         test_path_is_missing $infodir/commit-graph &&
 151         test_path_is_file $graphdir/commit-graph-chain &&
 152         ls $graphdir/graph-*.graph >graph-files &&
 153         test_line_count = 3 graph-files &&
 154         verify_chain_files_exist $graphdir
 155 '
 156
 157 graph_git_behavior 'three-layer commit-graph: commit 11 vs 6' commits/11 commits/6
 158
 159 test_expect_success 'add one commit, write a merged graph' '
 160         test_commit 12 &&
 161         git branch commits/12 &&
 162         git commit-graph write --reachable --split &&
 163         test_path_is_file $graphdir/commit-graph-chain &&
 164         test_line_count = 2 $graphdir/commit-graph-chain &&
 165         ls $graphdir/graph-*.graph >graph-files &&
 166         test_line_count = 2 graph-files &&
 167         verify_chain_files_exist $graphdir
 168 '
 169
 170 graph_git_behavior 'merged commit-graph: commit 12 vs 6' commits/12 commits/6
 171
 172 test_expect_success 'create fork and chain across alternate' '
 173         git clone . fork &&
 174         (
 175                 cd fork &&
 176                 git config core.commitGraph true &&
 177                 rm -rf $graphdir &&
 178                 echo "$(pwd)/../.git/objects" >.git/objects/info/alternates &&
 179                 test_commit 13 &&
 180                 git branch commits/13 &&
 181                 git commit-graph write --reachable --split &&
 182                 test_path_is_file $graphdir/commit-graph-chain &&
 183                 test_line_count = 3 $graphdir/commit-graph-chain &&
 184                 ls $graphdir/graph-*.graph >graph-files &&
 185                 test_line_count = 1 graph-files &&
 186                 git -c core.commitGraph=true  rev-list HEAD >expect &&
 187                 git -c core.commitGraph=false rev-list HEAD >actual &&
 188                 test_cmp expect actual &&
 189                 test_commit 14 &&
 190                 git commit-graph write --reachable --split --object-dir=.git/objects/ &&
 191                 test_line_count = 3 $graphdir/commit-graph-chain &&
 192                 ls $graphdir/graph-*.graph >graph-files &&
 193                 test_line_count = 1 graph-files
 194         )
 195 '
 196
 197 if test -d fork
 198 then
 199         graph_git_behavior 'alternate: commit 13 vs 6' commits/13 origin/commits/6 "fork"
 200 fi
 201
 202 test_expect_success 'test merge stragety constants' '
 203         git clone . merge-2 &&
 204         (
 205                 cd merge-2 &&
 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=2 &&
 210                 test_line_count = 3 $graphdir/commit-graph-chain
 211
 212         ) &&
 213         git clone . merge-10 &&
 214         (
 215                 cd merge-10 &&
 216                 git config core.commitGraph true &&
 217                 test_line_count = 2 $graphdir/commit-graph-chain &&
 218                 test_commit 14 &&
 219                 git commit-graph write --reachable --split --size-multiple=10 &&
 220                 test_line_count = 1 $graphdir/commit-graph-chain &&
 221                 ls $graphdir/graph-*.graph >graph-files &&
 222                 test_line_count = 1 graph-files
 223         ) &&
 224         git clone . merge-10-expire &&
 225         (
 226                 cd merge-10-expire &&
 227                 git config core.commitGraph true &&
 228                 test_line_count = 2 $graphdir/commit-graph-chain &&
 229                 test_commit 15 &&
 230                 touch $graphdir/to-delete.graph $graphdir/to-keep.graph &&
 231                 test-tool chmtime =1546362000 $graphdir/to-delete.graph &&
 232                 test-tool chmtime =1546362001 $graphdir/to-keep.graph &&
 233                 git commit-graph write --reachable --split --size-multiple=10 \
 234                         --expire-time="2019-01-01 12:00 -05:00" &&
 235                 test_line_count = 1 $graphdir/commit-graph-chain &&
 236                 test_path_is_missing $graphdir/to-delete.graph &&
 237                 test_path_is_file $graphdir/to-keep.graph &&
 238                 ls $graphdir/graph-*.graph >graph-files &&
 239                 test_line_count = 3 graph-files
 240         ) &&
 241         git clone --no-hardlinks . max-commits &&
 242         (
 243                 cd max-commits &&
 244                 git config core.commitGraph true &&
 245                 test_line_count = 2 $graphdir/commit-graph-chain &&
 246                 test_commit 16 &&
 247                 test_commit 17 &&
 248                 git commit-graph write --reachable --split --max-commits=1 &&
 249                 test_line_count = 1 $graphdir/commit-graph-chain &&
 250                 ls $graphdir/graph-*.graph >graph-files &&
 251                 test_line_count = 1 graph-files
 252         )
 253 '
 254
 255 test_expect_success 'remove commit-graph-chain file after flattening' '
 256         git clone . flatten &&
 257         (
 258                 cd flatten &&
 259                 test_line_count = 2 $graphdir/commit-graph-chain &&
 260                 git commit-graph write --reachable &&
 261                 test_path_is_missing $graphdir/commit-graph-chain &&
 262                 ls $graphdir >graph-files &&
 263                 test_line_count = 0 graph-files
 264         )
 265 '
 266
 267 corrupt_file() {
 268         file=$1
 269         pos=$2
 270         data="${3:-\0}"
 271         chmod a+w "$file" &&
 272         printf "$data" | dd of="$file" bs=1 seek="$pos" conv=notrunc
 273 }
 274
 275 test_expect_success 'verify hashes along chain, even in shallow' '
 276         git clone --no-hardlinks . verify &&
 277         (
 278                 cd verify &&
 279                 git commit-graph verify &&
 280                 base_file=$graphdir/graph-$(head -n 1 $graphdir/commit-graph-chain).graph &&
 281                 corrupt_file "$base_file" $(test_oid shallow) "\01" &&
 282                 test_must_fail git commit-graph verify --shallow 2>test_err &&
 283                 grep -v "^+" test_err >err &&
 284                 test_i18ngrep "incorrect checksum" err
 285         )
 286 '
 287
 288 test_expect_success 'verify --shallow does not check base contents' '
 289         git clone --no-hardlinks . verify-shallow &&
 290         (
 291                 cd verify-shallow &&
 292                 git commit-graph verify &&
 293                 base_file=$graphdir/graph-$(head -n 1 $graphdir/commit-graph-chain).graph &&
 294                 corrupt_file "$base_file" 1000 "\01" &&
 295                 git commit-graph verify --shallow &&
 296                 test_must_fail git commit-graph verify 2>test_err &&
 297                 grep -v "^+" test_err >err &&
 298                 test_i18ngrep "incorrect checksum" err
 299         )
 300 '
 301
 302 test_expect_success 'warn on base graph chunk incorrect' '
 303         git clone --no-hardlinks . base-chunk &&
 304         (
 305                 cd base-chunk &&
 306                 git commit-graph verify &&
 307                 base_file=$graphdir/graph-$(tail -n 1 $graphdir/commit-graph-chain).graph &&
 308                 corrupt_file "$base_file" $(test_oid base) "\01" &&
 309                 git commit-graph verify --shallow 2>test_err &&
 310                 grep -v "^+" test_err >err &&
 311                 test_i18ngrep "commit-graph chain does not match" err
 312         )
 313 '
 314
 315 test_expect_success 'verify after commit-graph-chain corruption' '
 316         git clone --no-hardlinks . verify-chain &&
 317         (
 318                 cd verify-chain &&
 319                 corrupt_file "$graphdir/commit-graph-chain" 60 "G" &&
 320                 git commit-graph verify 2>test_err &&
 321                 grep -v "^+" test_err >err &&
 322                 test_i18ngrep "invalid commit-graph chain" err &&
 323                 corrupt_file "$graphdir/commit-graph-chain" 60 "A" &&
 324                 git commit-graph verify 2>test_err &&
 325                 grep -v "^+" test_err >err &&
 326                 test_i18ngrep "unable to find all commit-graph files" err
 327         )
 328 '
 329
 330 test_expect_success 'verify across alternates' '
 331         git clone --no-hardlinks . verify-alt &&
 332         (
 333                 cd verify-alt &&
 334                 rm -rf $graphdir &&
 335                 altdir="$(pwd)/../.git/objects" &&
 336                 echo "$altdir" >.git/objects/info/alternates &&
 337                 git commit-graph verify --object-dir="$altdir/" &&
 338                 test_commit extra &&
 339                 git commit-graph write --reachable --split &&
 340                 tip_file=$graphdir/graph-$(tail -n 1 $graphdir/commit-graph-chain).graph &&
 341                 corrupt_file "$tip_file" 100 "\01" &&
 342                 test_must_fail git commit-graph verify --shallow 2>test_err &&
 343                 grep -v "^+" test_err >err &&
 344                 test_i18ngrep "commit-graph has incorrect fanout value" err
 345         )
 346 '
 347
 348 test_expect_success 'add octopus merge' '
 349         git reset --hard commits/10 &&
 350         git merge commits/3 commits/4 &&
 351         git branch merge/octopus &&
 352         git commit-graph write --reachable --split &&
 353         git commit-graph verify --progress 2>err &&
 354         test_line_count = 1 err &&
 355         grep "Verifying commits in commit graph: 100% (18/18)" err &&
 356         test_i18ngrep ! warning err &&
 357         test_line_count = 3 $graphdir/commit-graph-chain
 358 '
 359
 360 graph_git_behavior 'graph exists' merge/octopus commits/12
 361
 362 test_expect_success 'split across alternate where alternate is not split' '
 363         git commit-graph write --reachable &&
 364         test_path_is_file .git/objects/info/commit-graph &&
 365         cp .git/objects/info/commit-graph . &&
 366         git clone --no-hardlinks . alt-split &&
 367         (
 368                 cd alt-split &&
 369                 rm -f .git/objects/info/commit-graph &&
 370                 echo "$(pwd)"/../.git/objects >.git/objects/info/alternates &&
 371                 test_commit 18 &&
 372                 git commit-graph write --reachable --split &&
 373                 test_line_count = 1 $graphdir/commit-graph-chain
 374         ) &&
 375         test_cmp commit-graph .git/objects/info/commit-graph
 376 '
 377
 378 test_expect_success '--split=no-merge always writes an incremental' '
 379         test_when_finished rm -rf a b &&
 380         rm -rf $graphdir $infodir/commit-graph &&
 381         git reset --hard commits/2 &&
 382         git rev-list HEAD~1 >a &&
 383         git rev-list HEAD >b &&
 384         git commit-graph write --split --stdin-commits <a &&
 385         git commit-graph write --split=no-merge --stdin-commits <b &&
 386         test_line_count = 2 $graphdir/commit-graph-chain
 387 '
 388
 389 test_expect_success '--split=replace replaces the chain' '
 390         rm -rf $graphdir $infodir/commit-graph &&
 391         git reset --hard commits/3 &&
 392         git rev-list -1 HEAD~2 >a &&
 393         git rev-list -1 HEAD~1 >b &&
 394         git rev-list -1 HEAD >c &&
 395         git commit-graph write --split=no-merge --stdin-commits <a &&
 396         git commit-graph write --split=no-merge --stdin-commits <b &&
 397         git commit-graph write --split=no-merge --stdin-commits <c &&
 398         test_line_count = 3 $graphdir/commit-graph-chain &&
 399         git commit-graph write --stdin-commits --split=replace <b &&
 400         test_path_is_missing $infodir/commit-graph &&
 401         test_path_is_file $graphdir/commit-graph-chain &&
 402         ls $graphdir/graph-*.graph >graph-files &&
 403         test_line_count = 1 graph-files &&
 404         verify_chain_files_exist $graphdir &&
 405         graph_read_expect 2
 406 '
 407
 408 test_expect_success ULIMIT_FILE_DESCRIPTORS 'handles file descriptor exhaustion' '
 409         git init ulimit &&
 410         (
 411                 cd ulimit &&
 412                 for i in $(test_seq 64)
 413                 do
 414                         test_commit $i &&
 415                         run_with_limited_open_files test_might_fail git commit-graph write \
 416                                 --split=no-merge --reachable || return 1
 417                 done
 418         )
 419 '
 420
 421 while read mode modebits
 422 do
 423         test_expect_success POSIXPERM "split commit-graph respects core.sharedrepository $mode" '
 424                 rm -rf $graphdir $infodir/commit-graph &&
 425                 git reset --hard commits/1 &&
 426                 test_config core.sharedrepository "$mode" &&
 427                 git commit-graph write --split --reachable &&
 428                 ls $graphdir/graph-*.graph >graph-files &&
 429                 test_line_count = 1 graph-files &&
 430                 echo "$modebits" >expect &&
 431                 test_modebits $graphdir/graph-*.graph >actual &&
 432                 test_cmp expect actual &&
 433                 test_modebits $graphdir/commit-graph-chain >actual &&
 434                 test_cmp expect actual
 435         '
 436 done <<\EOF
 437 0666 -r--r--r--
 438 0600 -r--------
 439 EOF
 440
 441 test_expect_success '--split=replace with partial Bloom data' '
 442         rm -rf $graphdir $infodir/commit-graph &&
 443         git reset --hard commits/3 &&
 444         git rev-list -1 HEAD~2 >a &&
 445         git rev-list -1 HEAD~1 >b &&
 446         git commit-graph write --split=no-merge --stdin-commits --changed-paths <a &&
 447         git commit-graph write --split=no-merge --stdin-commits <b &&
 448         git commit-graph write --split=replace --stdin-commits --changed-paths <c &&
 449         ls $graphdir/graph-*.graph >graph-files &&
 450         test_line_count = 1 graph-files &&
 451         verify_chain_files_exist $graphdir
 452 '
 453
 454 test_expect_success 'prevent regression for duplicate commits across layers' '
 455         git init dup &&
 456         git -C dup commit --allow-empty -m one &&
 457         git -C dup -c core.commitGraph=false commit-graph write --split=no-merge --reachable 2>err &&
 458         test_i18ngrep "attempting to write a commit-graph" err &&
 459         git -C dup commit-graph write --split=no-merge --reachable &&
 460         git -C dup commit --allow-empty -m two &&
 461         git -C dup commit-graph write --split=no-merge --reachable &&
 462         git -C dup commit --allow-empty -m three &&
 463         git -C dup commit-graph write --split --reachable &&
 464         git -C dup commit-graph verify
 465 '
 466
 467 NUM_FIRST_LAYER_COMMITS=64
 468 NUM_SECOND_LAYER_COMMITS=16
 469 NUM_THIRD_LAYER_COMMITS=7
 470 NUM_FOURTH_LAYER_COMMITS=8
 471 NUM_FIFTH_LAYER_COMMITS=16
 472 SECOND_LAYER_SEQUENCE_START=$(($NUM_FIRST_LAYER_COMMITS + 1))
 473 SECOND_LAYER_SEQUENCE_END=$(($SECOND_LAYER_SEQUENCE_START + $NUM_SECOND_LAYER_COMMITS - 1))
 474 THIRD_LAYER_SEQUENCE_START=$(($SECOND_LAYER_SEQUENCE_END + 1))
 475 THIRD_LAYER_SEQUENCE_END=$(($THIRD_LAYER_SEQUENCE_START + $NUM_THIRD_LAYER_COMMITS - 1))
 476 FOURTH_LAYER_SEQUENCE_START=$(($THIRD_LAYER_SEQUENCE_END + 1))
 477 FOURTH_LAYER_SEQUENCE_END=$(($FOURTH_LAYER_SEQUENCE_START + $NUM_FOURTH_LAYER_COMMITS - 1))
 478 FIFTH_LAYER_SEQUENCE_START=$(($FOURTH_LAYER_SEQUENCE_END + 1))
 479 FIFTH_LAYER_SEQUENCE_END=$(($FIFTH_LAYER_SEQUENCE_START + $NUM_FIFTH_LAYER_COMMITS - 1))
 480
 481 # Current split graph chain:
 482 #
 483 #     16 commits (No GDAT)
 484 # ------------------------
 485 #     64 commits (GDAT)
 486 #
 487 test_expect_success 'setup repo for mixed generation commit-graph-chain' '
 488         graphdir=".git/objects/info/commit-graphs" &&
 489         test_oid_cache <<-EOF &&
 490         oid_version sha1:1
 491         oid_version sha256:2
 492         EOF
 493         git init mixed &&
 494         (
 495                 cd mixed &&
 496                 git config core.commitGraph true &&
 497                 git config gc.writeCommitGraph false &&
 498                 for i in $(test_seq $NUM_FIRST_LAYER_COMMITS)
 499                 do
 500                         test_commit $i &&
 501                         git branch commits/$i || return 1
 502                 done &&
 503                 git -c commitGraph.generationVersion=2 commit-graph write --reachable --split &&
 504                 graph_read_expect $NUM_FIRST_LAYER_COMMITS &&
 505                 test_line_count = 1 $graphdir/commit-graph-chain &&
 506                 for i in $(test_seq $SECOND_LAYER_SEQUENCE_START $SECOND_LAYER_SEQUENCE_END)
 507                 do
 508                         test_commit $i &&
 509                         git branch commits/$i || return 1
 510                 done &&
 511                 git -c commitGraph.generationVersion=1 commit-graph write --reachable --split=no-merge &&
 512                 test_line_count = 2 $graphdir/commit-graph-chain &&
 513                 test-tool read-graph >output &&
 514                 cat >expect <<-EOF &&
 515                 header: 43475048 1 $(test_oid oid_version) 4 1
 516                 num_commits: $NUM_SECOND_LAYER_COMMITS
 517                 chunks: oid_fanout oid_lookup commit_metadata
 518                 options:
 519                 EOF
 520                 test_cmp expect output &&
 521                 git commit-graph verify &&
 522                 cat $graphdir/commit-graph-chain
 523         )
 524 '
 525
 526 # The new layer will be added without generation data chunk as it was not
 527 # present on the layer underneath it.
 528 #
 529 #      7 commits (No GDAT)
 530 # ------------------------
 531 #     16 commits (No GDAT)
 532 # ------------------------
 533 #     64 commits (GDAT)
 534 #
 535 test_expect_success 'do not write generation data chunk if not present on existing tip' '
 536         git clone mixed mixed-no-gdat &&
 537         (
 538                 cd mixed-no-gdat &&
 539                 for i in $(test_seq $THIRD_LAYER_SEQUENCE_START $THIRD_LAYER_SEQUENCE_END)
 540                 do
 541                         test_commit $i &&
 542                         git branch commits/$i || return 1
 543                 done &&
 544                 git commit-graph write --reachable --split=no-merge &&
 545                 test_line_count = 3 $graphdir/commit-graph-chain &&
 546                 test-tool read-graph >output &&
 547                 cat >expect <<-EOF &&
 548                 header: 43475048 1 $(test_oid oid_version) 4 2
 549                 num_commits: $NUM_THIRD_LAYER_COMMITS
 550                 chunks: oid_fanout oid_lookup commit_metadata
 551                 options:
 552                 EOF
 553                 test_cmp expect output &&
 554                 git commit-graph verify
 555         )
 556 '
 557
 558 # Number of commits in each layer of the split-commit graph before merge:
 559 #
 560 #      8 commits (No GDAT)
 561 # ------------------------
 562 #      7 commits (No GDAT)
 563 # ------------------------
 564 #     16 commits (No GDAT)
 565 # ------------------------
 566 #     64 commits (GDAT)
 567 #
 568 # The top two layers are merged and do not have generation data chunk as layer below them does
 569 # not have generation data chunk.
 570 #
 571 #     15 commits (No GDAT)
 572 # ------------------------
 573 #     16 commits (No GDAT)
 574 # ------------------------
 575 #     64 commits (GDAT)
 576 #
 577 test_expect_success 'do not write generation data chunk if the topmost remaining layer does not have generation data chunk' '
 578         git clone mixed-no-gdat mixed-merge-no-gdat &&
 579         (
 580                 cd mixed-merge-no-gdat &&
 581                 for i in $(test_seq $FOURTH_LAYER_SEQUENCE_START $FOURTH_LAYER_SEQUENCE_END)
 582                 do
 583                         test_commit $i &&
 584                         git branch commits/$i || return 1
 585                 done &&
 586                 git commit-graph write --reachable --split --size-multiple 1 &&
 587                 test_line_count = 3 $graphdir/commit-graph-chain &&
 588                 test-tool read-graph >output &&
 589                 cat >expect <<-EOF &&
 590                 header: 43475048 1 $(test_oid oid_version) 4 2
 591                 num_commits: $(($NUM_THIRD_LAYER_COMMITS + $NUM_FOURTH_LAYER_COMMITS))
 592                 chunks: oid_fanout oid_lookup commit_metadata
 593                 options:
 594                 EOF
 595                 test_cmp expect output &&
 596                 git commit-graph verify
 597         )
 598 '
 599
 600 # Number of commits in each layer of the split-commit graph before merge:
 601 #
 602 #     16 commits (No GDAT)
 603 # ------------------------
 604 #     15 commits (No GDAT)
 605 # ------------------------
 606 #     16 commits (No GDAT)
 607 # ------------------------
 608 #     64 commits (GDAT)
 609 #
 610 # The top three layers are merged and has generation data chunk as the topmost remaining layer
 611 # has generation data chunk.
 612 #
 613 #     47 commits (GDAT)
 614 # ------------------------
 615 #     64 commits (GDAT)
 616 #
 617 test_expect_success 'write generation data chunk if topmost remaining layer has generation data chunk' '
 618         git clone mixed-merge-no-gdat mixed-merge-gdat &&
 619         (
 620                 cd mixed-merge-gdat &&
 621                 for i in $(test_seq $FIFTH_LAYER_SEQUENCE_START $FIFTH_LAYER_SEQUENCE_END)
 622                 do
 623                         test_commit $i &&
 624                         git branch commits/$i || return 1
 625                 done &&
 626                 git commit-graph write --reachable --split --size-multiple 1 &&
 627                 test_line_count = 2 $graphdir/commit-graph-chain &&
 628                 test-tool read-graph >output &&
 629                 cat >expect <<-EOF &&
 630                 header: 43475048 1 $(test_oid oid_version) 5 1
 631                 num_commits: $(($NUM_SECOND_LAYER_COMMITS + $NUM_THIRD_LAYER_COMMITS + $NUM_FOURTH_LAYER_COMMITS + $NUM_FIFTH_LAYER_COMMITS))
 632                 chunks: oid_fanout oid_lookup commit_metadata generation_data
 633                 options: read_generation_data
 634                 EOF
 635                 test_cmp expect output
 636         )
 637 '
 638
 639 test_expect_success 'write generation data chunk when commit-graph chain is replaced' '
 640         git clone mixed mixed-replace &&
 641         (
 642                 cd mixed-replace &&
 643                 git commit-graph write --reachable --split=replace &&
 644                 test_path_is_file $graphdir/commit-graph-chain &&
 645                 test_line_count = 1 $graphdir/commit-graph-chain &&
 646                 verify_chain_files_exist $graphdir &&
 647                 graph_read_expect $(($NUM_FIRST_LAYER_COMMITS + $NUM_SECOND_LAYER_COMMITS)) &&
 648                 git commit-graph verify
 649         )
 650 '
 651
 652 test_done