lib/commit_graph.c

   1 /*
   2  * Copyright (c) 2018, 2019, 2020 Stefan Sperling <stsp@openbsd.org>
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15  */
  16
  17 #include <sys/types.h>
  18 #include <sys/stat.h>
  19 #include <sys/queue.h>
  20
  21 #include <limits.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <zlib.h>
  26 #include <ctype.h>
  27
  28 #include "got_compat.h"
  29
  30 #include "got_error.h"
  31 #include "got_object.h"
  32 #include "got_cancel.h"
  33 #include "got_commit_graph.h"
  34 #include "got_path.h"
  35
  36 #include "got_lib_delta.h"
  37 #include "got_lib_inflate.h"
  38 #include "got_lib_object.h"
  39 #include "got_lib_object_idset.h"
  40
  41 struct got_commit_graph_node {
  42         struct got_object_id id;
  43
  44         /* Used only during iteration. */
  45         time_t timestamp;
  46         TAILQ_ENTRY(got_commit_graph_node) entry;
  47 };
  48
  49 TAILQ_HEAD(got_commit_graph_iter_list, got_commit_graph_node);
  50
  51 struct got_commit_graph_branch_tip {
  52         struct got_object_id *commit_id;
  53         struct got_commit_object *commit;
  54         struct got_commit_graph_node *new_node;
  55 };
  56
  57 struct got_commit_graph {
  58         /* The set of all commits we have traversed. */
  59         struct got_object_idset *node_ids;
  60
  61         int flags;
  62 #define GOT_COMMIT_GRAPH_FIRST_PARENT_TRAVERSAL         0x01
  63
  64         /*
  65          * A set of object IDs of known parent commits which we have not yet
  66          * traversed. Each commit ID in this set represents a branch in commit
  67          * history: Either the first-parent branch of the head node, or another
  68          * branch corresponding to a traversed merge commit for which we have
  69          * not traversed a branch point commit yet.
  70          *
  71          * Whenever we add a commit with a matching ID to the graph, we remove
  72          * its corresponding element from this set, and add new elements for
  73          * each of that commit's parent commits which were not traversed yet.
  74          *
  75          * When API users ask us to fetch more commits, we fetch commits from
  76          * all currently open branches. This allows API users to process
  77          * commits in linear order even though the history contains branches.
  78          */
  79         struct got_object_idset *open_branches;
  80
  81         /* Array of branch tips for fetch_commits_from_open_branches(). */
  82         struct got_commit_graph_branch_tip *tips;
  83         int ntips;
  84
  85         /* Path of tree entry of interest to the API user. */
  86         char *path;
  87
  88         /*
  89          * Nodes which will be passed to the API user next, sorted by
  90          * commit timestmap.
  91          */
  92         struct got_commit_graph_iter_list iter_list;
  93 };
  94
  95 static const struct got_error *
  96 detect_changed_path(int *changed, struct got_commit_object *commit,
  97     struct got_object_id *commit_id, const char *path,
  98     struct got_repository *repo)
  99 {
 100         const struct got_error *err = NULL;
 101         struct got_commit_object *pcommit = NULL;
 102         struct got_tree_object *tree = NULL, *ptree = NULL;
 103         struct got_object_qid *pid;
 104
 105         if (got_path_is_root_dir(path)) {
 106                 *changed = 1;
 107                 return NULL;
 108         }
 109
 110         *changed = 0;
 111
 112         pid = STAILQ_FIRST(&commit->parent_ids);
 113         if (pid == NULL) {
 114                 struct got_object_id *obj_id;
 115                 err = got_object_id_by_path(&obj_id, repo, commit, path);
 116                 if (err) {
 117                         if (err->code == GOT_ERR_NO_TREE_ENTRY)
 118                                 err = NULL;
 119                 } else
 120                         *changed = 1; /* The path was created in this commit. */
 121                 free(obj_id);
 122                 return err;
 123         }
 124
 125         err = got_object_open_as_tree(&tree, repo, commit->tree_id);
 126         if (err)
 127                 return err;
 128
 129         err = got_object_open_as_commit(&pcommit, repo, &pid->id);
 130         if (err)
 131                 goto done;
 132
 133         err = got_object_open_as_tree(&ptree, repo, pcommit->tree_id);
 134         if (err)
 135                 goto done;
 136
 137         err = got_object_tree_path_changed(changed, tree, ptree, path, repo);
 138 done:
 139         if (tree)
 140                 got_object_tree_close(tree);
 141         if (ptree)
 142                 got_object_tree_close(ptree);
 143         if (pcommit)
 144                 got_object_commit_close(pcommit);
 145         return err;
 146 }
 147
 148 static void
 149 add_node_to_iter_list(struct got_commit_graph *graph,
 150     struct got_commit_graph_node *node, time_t committer_time)
 151 {
 152         struct got_commit_graph_node *n, *next;
 153
 154         node->timestamp = committer_time;
 155
 156         n = TAILQ_FIRST(&graph->iter_list);
 157         while (n) {
 158                 next = TAILQ_NEXT(n, entry);
 159                 if (next && node->timestamp >= next->timestamp) {
 160                         TAILQ_INSERT_BEFORE(next, node, entry);
 161                         return;
 162                 }
 163                 n = next;
 164         }
 165         TAILQ_INSERT_TAIL(&graph->iter_list, node, entry);
 166 }
 167
 168 static const struct got_error *
 169 add_node(struct got_commit_graph_node **new_node,
 170     struct got_commit_graph *graph, struct got_object_id *commit_id,
 171     struct got_repository *repo)
 172 {
 173         const struct got_error *err = NULL;
 174         struct got_commit_graph_node *node;
 175
 176         *new_node = NULL;
 177
 178         node = calloc(1, sizeof(*node));
 179         if (node == NULL)
 180                 return got_error_from_errno("calloc");
 181
 182         memcpy(&node->id, commit_id, sizeof(node->id));
 183         err = got_object_idset_add(graph->node_ids, &node->id, NULL);
 184         if (err)
 185                 free(node);
 186         else
 187                 *new_node = node;
 188         return err;
 189 }
 190
 191 /*
 192  * Ask got-read-pack to traverse first-parent history until a commit is
 193  * encountered which modified graph->path, or until the pack file runs
 194  * out of relevant commits. This is faster than sending an individual
 195  * request for each commit stored in the pack file.
 196  */
 197 static const struct got_error *
 198 packed_first_parent_traversal(int *ncommits_traversed,
 199     struct got_commit_graph *graph, struct got_object_id *commit_id,
 200     struct got_repository *repo)
 201 {
 202         const struct got_error *err = NULL;
 203         struct got_object_id_queue traversed_commits;
 204         struct got_object_qid *qid;
 205
 206         STAILQ_INIT(&traversed_commits);
 207         *ncommits_traversed = 0;
 208
 209         err = got_traverse_packed_commits(&traversed_commits,
 210             commit_id, graph->path, repo);
 211         if (err)
 212                 return err;
 213
 214         /* Add all traversed commits to the graph... */
 215         STAILQ_FOREACH(qid, &traversed_commits, entry) {
 216                 if (got_object_idset_contains(graph->open_branches, &qid->id))
 217                         continue;
 218                 if (got_object_idset_contains(graph->node_ids, &qid->id))
 219                         continue;
 220
 221                 (*ncommits_traversed)++;
 222
 223                 /* ... except the last commit is the new branch tip. */
 224                 if (STAILQ_NEXT(qid, entry) == NULL) {
 225                         err = got_object_idset_add(graph->open_branches,
 226                             &qid->id, NULL);
 227                         break;
 228                 }
 229
 230                 err = got_object_idset_add(graph->node_ids, &qid->id, NULL);
 231                 if (err)
 232                         break;
 233         }
 234
 235         got_object_id_queue_free(&traversed_commits);
 236         return err;
 237 }
 238
 239 static const struct got_error *
 240 close_branch(struct got_commit_graph *graph, struct got_object_id *commit_id)
 241 {
 242         const struct got_error *err;
 243
 244         err = got_object_idset_remove(NULL, graph->open_branches, commit_id);
 245         if (err && err->code != GOT_ERR_NO_OBJ)
 246                 return err;
 247         return NULL;
 248 }
 249
 250 static const struct got_error *
 251 advance_branch(struct got_commit_graph *graph, struct got_object_id *commit_id,
 252     struct got_commit_object *commit, struct got_repository *repo)
 253 {
 254         const struct got_error *err;
 255         struct got_object_qid *qid;
 256         struct got_object_id *merged_id = NULL;
 257
 258         err = close_branch(graph, commit_id);
 259         if (err)
 260                 return err;
 261
 262         if (graph->flags & GOT_COMMIT_GRAPH_FIRST_PARENT_TRAVERSAL) {
 263                 qid = STAILQ_FIRST(&commit->parent_ids);
 264                 if (qid == NULL ||
 265                     got_object_idset_contains(graph->open_branches, &qid->id))
 266                         return NULL;
 267                 /*
 268                  * The root directory always changes by definition, and when
 269                  * logging the root we want to traverse consecutive commits
 270                  * even if they point at the same tree.
 271                  * But if we are looking for a specific path then we can avoid
 272                  * fetching packed commits which did not modify the path and
 273                  * only fetch their IDs. This speeds up 'got blame'.
 274                  */
 275                 if (!got_path_is_root_dir(graph->path) &&
 276                     (commit->flags & GOT_COMMIT_FLAG_PACKED)) {
 277                         int ncommits = 0;
 278                         err = packed_first_parent_traversal(&ncommits,
 279                             graph, &qid->id, repo);
 280                         if (err || ncommits > 0)
 281                                 return err;
 282                 }
 283                 return got_object_idset_add(graph->open_branches,
 284                     &qid->id, NULL);
 285         }
 286
 287         /*
 288          * If we are graphing commits for a specific path, skip branches
 289          * which do not contribute any content to this path.
 290          */
 291         if (commit->nparents > 1 && !got_path_is_root_dir(graph->path)) {
 292                 err = got_object_id_by_path(&merged_id, repo, commit, graph->path);
 293                 if (err && err->code != GOT_ERR_NO_TREE_ENTRY)
 294                         return err;
 295                 /* The requested path does not exist in this merge commit. */
 296         }
 297         if (commit->nparents > 1 && !got_path_is_root_dir(graph->path) &&
 298             merged_id != NULL) {
 299                 struct got_object_id *prev_id = NULL;
 300                 int branches_differ = 0;
 301
 302
 303                 STAILQ_FOREACH(qid, &commit->parent_ids, entry) {
 304                         struct got_object_id *id = NULL;
 305                         struct got_commit_object *pcommit = NULL;
 306
 307                         if (got_object_idset_contains(graph->open_branches,
 308                             &qid->id))
 309                                 continue;
 310
 311                         err = got_object_open_as_commit(&pcommit, repo,
 312                             &qid->id);
 313                         if (err) {
 314                                 free(merged_id);
 315                                 free(prev_id);
 316                                 return err;
 317                         }
 318                         err = got_object_id_by_path(&id, repo, pcommit,
 319                             graph->path);
 320                         got_object_commit_close(pcommit);
 321                         pcommit = NULL;
 322                         if (err) {
 323                                 if (err->code == GOT_ERR_NO_TREE_ENTRY) {
 324                                         branches_differ = 1;
 325                                         continue;
 326                                 }
 327                                 free(merged_id);
 328                                 free(prev_id);
 329                                 return err;
 330                         }
 331
 332                         if (prev_id) {
 333                                 if (!branches_differ &&
 334                                     got_object_id_cmp(id, prev_id) != 0)
 335                                         branches_differ = 1;
 336                                 free(prev_id);
 337                         }
 338                         prev_id = id;
 339
 340                         /*
 341                          * If a branch has created the merged content we can
 342                          * skip any other branches.
 343                          */
 344                         if (got_object_id_cmp(merged_id, id) == 0) {
 345                                 err = got_object_idset_add(graph->open_branches,
 346                                     &qid->id, NULL);
 347                                 free(merged_id);
 348                                 free(id);
 349                                 return err;
 350                         }
 351                 }
 352
 353                 free(prev_id);
 354                 prev_id = NULL;
 355                 free(merged_id);
 356                 merged_id = NULL;
 357
 358                 /*
 359                  * If the path's content is the same on all branches,
 360                  * follow the first parent only.
 361                  */
 362                 if (!branches_differ) {
 363                         qid = STAILQ_FIRST(&commit->parent_ids);
 364                         if (qid == NULL)
 365                                 return NULL;
 366                         if (got_object_idset_contains(graph->open_branches,
 367                             &qid->id))
 368                                 return NULL;
 369                         if (got_object_idset_contains(graph->node_ids,
 370                             &qid->id))
 371                                 return NULL; /* parent already traversed */
 372                         return got_object_idset_add(graph->open_branches,
 373                             &qid->id, NULL);
 374                 }
 375         }
 376
 377         STAILQ_FOREACH(qid, &commit->parent_ids, entry) {
 378                 if (got_object_idset_contains(graph->open_branches, &qid->id))
 379                         continue;
 380                 if (got_object_idset_contains(graph->node_ids, &qid->id))
 381                         continue; /* parent already traversed */
 382                 err = got_object_idset_add(graph->open_branches, &qid->id,
 383                     NULL);
 384                 if (err)
 385                         return err;
 386         }
 387
 388         return NULL;
 389 }
 390
 391 const struct got_error *
 392 got_commit_graph_open(struct got_commit_graph **graph,
 393     const char *path, int first_parent_traversal)
 394 {
 395         const struct got_error *err = NULL;
 396
 397         *graph = calloc(1, sizeof(**graph));
 398         if (*graph == NULL)
 399                 return got_error_from_errno("calloc");
 400
 401         TAILQ_INIT(&(*graph)->iter_list);
 402
 403         (*graph)->path = strdup(path);
 404         if ((*graph)->path == NULL) {
 405                 err = got_error_from_errno("strdup");
 406                 goto done;
 407         }
 408
 409         (*graph)->node_ids = got_object_idset_alloc();
 410         if ((*graph)->node_ids == NULL) {
 411                 err = got_error_from_errno("got_object_idset_alloc");
 412                 goto done;
 413         }
 414
 415         (*graph)->open_branches = got_object_idset_alloc();
 416         if ((*graph)->open_branches == NULL) {
 417                 err = got_error_from_errno("got_object_idset_alloc");
 418                 goto done;
 419         }
 420
 421         if (first_parent_traversal)
 422                 (*graph)->flags |= GOT_COMMIT_GRAPH_FIRST_PARENT_TRAVERSAL;
 423 done:
 424         if (err) {
 425                 got_commit_graph_close(*graph);
 426                 *graph = NULL;
 427         }
 428         return err;
 429 }
 430
 431 struct add_branch_tip_arg {
 432         struct got_commit_graph_branch_tip *tips;
 433         int ntips;
 434         struct got_repository *repo;
 435         struct got_commit_graph *graph;
 436 };
 437
 438 static const struct got_error *
 439 add_branch_tip(struct got_object_id *commit_id, void *data, void *arg)
 440 {
 441         const struct got_error *err;
 442         struct add_branch_tip_arg *a = arg;
 443         struct got_commit_graph_node *new_node;
 444         struct got_commit_object *commit;
 445
 446         err = got_object_open_as_commit(&commit, a->repo, commit_id);
 447         if (err)
 448                 return err;
 449
 450         err = add_node(&new_node, a->graph, commit_id, a->repo);
 451         if (err) {
 452                 got_object_commit_close(commit);
 453                 return err;
 454         }
 455
 456         a->tips[a->ntips].commit_id = &new_node->id;
 457         a->tips[a->ntips].commit = commit;
 458         a->tips[a->ntips].new_node = new_node;
 459         a->ntips++;
 460
 461         return NULL;
 462 }
 463
 464 static const struct got_error *
 465 fetch_commits_from_open_branches(struct got_commit_graph *graph,
 466     struct got_repository *repo, got_cancel_cb cancel_cb, void *cancel_arg)
 467 {
 468         const struct got_error *err;
 469         struct add_branch_tip_arg arg;
 470         int i, ntips;
 471
 472         ntips = got_object_idset_num_elements(graph->open_branches);
 473         if (ntips == 0)
 474                 return NULL;
 475
 476         /* (Re-)allocate branch tips array if necessary. */
 477         if (graph->ntips < ntips) {
 478                 struct got_commit_graph_branch_tip *tips;
 479                 tips = recallocarray(graph->tips, graph->ntips, ntips,
 480                     sizeof(*tips));
 481                 if (tips == NULL)
 482                         return got_error_from_errno("recallocarray");
 483                 graph->tips = tips;
 484                 graph->ntips = ntips;
 485         }
 486         arg.tips = graph->tips;
 487         arg.ntips = 0; /* add_branch_tip() will increment */
 488         arg.repo = repo;
 489         arg.graph = graph;
 490         err = got_object_idset_for_each(graph->open_branches, add_branch_tip,
 491             &arg);
 492         if (err)
 493                 goto done;
 494
 495         for (i = 0; i < arg.ntips; i++) {
 496                 struct got_object_id *commit_id;
 497                 struct got_commit_object *commit;
 498                 struct got_commit_graph_node *new_node;
 499                 int changed;
 500
 501                 if (cancel_cb) {
 502                         err = (*cancel_cb)(cancel_arg);
 503                         if (err)
 504                                 break;
 505                 }
 506
 507                 commit_id = arg.tips[i].commit_id;
 508                 commit = arg.tips[i].commit;
 509                 new_node = arg.tips[i].new_node;
 510
 511                 err = detect_changed_path(&changed, commit, commit_id,
 512                     graph->path, repo);
 513                 if (err) {
 514                         if (err->code != GOT_ERR_NO_OBJ)
 515                                 break;
 516                         /*
 517                          * History of the path stops here on the current
 518                          * branch. Keep going on other branches.
 519                          */
 520                         err = close_branch(graph, commit_id);
 521                         if (err)
 522                                 break;
 523                         continue;
 524                 }
 525                 if (changed) {
 526                         add_node_to_iter_list(graph, new_node,
 527                             got_object_commit_get_committer_time(commit));
 528                         arg.tips[i].new_node = NULL;
 529                 }
 530                 err = advance_branch(graph, commit_id, commit, repo);
 531                 if (err)
 532                         break;
 533         }
 534 done:
 535         for (i = 0; i < arg.ntips; i++) {
 536                 got_object_commit_close(arg.tips[i].commit);
 537                 free(arg.tips[i].new_node);
 538         }
 539         return err;
 540 }
 541
 542 void
 543 got_commit_graph_close(struct got_commit_graph *graph)
 544 {
 545         struct got_commit_graph_node *node;
 546
 547         while ((node = TAILQ_FIRST(&graph->iter_list))) {
 548                 TAILQ_REMOVE(&graph->iter_list, node, entry);
 549                 free(node);
 550         }
 551
 552         if (graph->open_branches)
 553                 got_object_idset_free(graph->open_branches);
 554         if (graph->node_ids)
 555                 got_object_idset_free(graph->node_ids);
 556         free(graph->tips);
 557         free(graph->path);
 558         free(graph);
 559 }
 560
 561 const struct got_error *
 562 got_commit_graph_iter_start(struct got_commit_graph *graph,
 563     struct got_object_id *id, struct got_repository *repo,
 564     got_cancel_cb cancel_cb, void *cancel_arg)
 565 {
 566         const struct got_error *err = NULL;
 567
 568         if (!TAILQ_EMPTY(&graph->iter_list))
 569                 return got_error(GOT_ERR_ITER_BUSY);
 570
 571         err = got_object_idset_add(graph->open_branches, id, NULL);
 572         if (err)
 573                 return err;
 574
 575         /* Locate first commit which changed graph->path. */
 576         while (TAILQ_EMPTY(&graph->iter_list) &&
 577             got_object_idset_num_elements(graph->open_branches) > 0) {
 578                 err = fetch_commits_from_open_branches(graph, repo,
 579                     cancel_cb, cancel_arg);
 580                 if (err)
 581                         return err;
 582         }
 583
 584         if (TAILQ_EMPTY(&graph->iter_list)) {
 585                 const char *path;
 586                 if (got_path_is_root_dir(graph->path))
 587                         return got_error_no_obj(id);
 588                 path = graph->path;
 589                 while (path[0] == '/')
 590                         path++;
 591                 return got_error_path(path, GOT_ERR_NO_TREE_ENTRY);
 592         }
 593
 594         return NULL;
 595 }
 596
 597 const struct got_error *
 598 got_commit_graph_iter_next(struct got_object_id *id,
 599     struct got_commit_graph *graph, struct got_repository *repo,
 600     got_cancel_cb cancel_cb, void *cancel_arg)
 601 {
 602         const struct got_error *err = NULL;
 603         struct got_commit_graph_node *node;
 604
 605         node = TAILQ_FIRST(&graph->iter_list);
 606         if (node == NULL) {
 607                 /* We are done iterating, or iteration was not started. */
 608                 return got_error(GOT_ERR_ITER_COMPLETED);
 609         }
 610
 611         while (TAILQ_NEXT(node, entry) == NULL &&
 612             got_object_idset_num_elements(graph->open_branches) > 0) {
 613                 err = fetch_commits_from_open_branches(graph, repo,
 614                     cancel_cb, cancel_arg);
 615                 if (err)
 616                         return err;
 617         }
 618
 619         memcpy(id, &node->id, sizeof(*id));
 620
 621         TAILQ_REMOVE(&graph->iter_list, node, entry);
 622         free(node);
 623         return NULL;
 624 }
 625
 626 static const struct got_error *
 627 find_yca_add_id(struct got_object_id **yca_id, struct got_commit_graph *graph,
 628     struct got_object_idset *commit_ids, struct got_repository *repo,
 629     got_cancel_cb cancel_cb, void *cancel_arg)
 630 {
 631         const struct got_error *err = NULL;
 632         struct got_object_id id;
 633
 634         err = got_commit_graph_iter_next(&id, graph, repo, cancel_cb,
 635             cancel_arg);
 636         if (err)
 637                 return err;
 638
 639         if (got_object_idset_contains(commit_ids, &id)) {
 640                 *yca_id = got_object_id_dup(&id);
 641                 if (*yca_id == NULL)
 642                         err = got_error_from_errno("got_object_id_dup");
 643                 return err;
 644         }
 645
 646         return got_object_idset_add(commit_ids, &id, NULL);
 647 }
 648
 649 /*
 650  * Sets *yca_id to the youngest common ancestor of commit_id and
 651  * commit_id2. Returns got_error(GOT_ERR_ANCESTRY) if they have no
 652  * common ancestors.
 653  *
 654  * If first_parent_traversal is nonzero, only linear history is considered.
 655  */
 656 const struct got_error *
 657 got_commit_graph_find_youngest_common_ancestor(struct got_object_id **yca_id,
 658     struct got_object_id *commit_id, struct got_object_id *commit_id2,
 659     int first_parent_traversal,
 660     struct got_repository *repo, got_cancel_cb cancel_cb, void *cancel_arg)
 661 {
 662         const struct got_error *err = NULL;
 663         struct got_commit_graph *graph = NULL, *graph2 = NULL;
 664         int completed = 0, completed2 = 0;
 665         struct got_object_idset *commit_ids;
 666
 667         *yca_id = NULL;
 668
 669         commit_ids = got_object_idset_alloc();
 670         if (commit_ids == NULL)
 671                 return got_error_from_errno("got_object_idset_alloc");
 672
 673         err = got_commit_graph_open(&graph, "/", first_parent_traversal);
 674         if (err)
 675                 goto done;
 676
 677         err = got_commit_graph_open(&graph2, "/", first_parent_traversal);
 678         if (err)
 679                 goto done;
 680
 681         err = got_commit_graph_iter_start(graph, commit_id, repo,
 682             cancel_cb, cancel_arg);
 683         if (err)
 684                 goto done;
 685
 686         err = got_commit_graph_iter_start(graph2, commit_id2, repo,
 687             cancel_cb, cancel_arg);
 688         if (err)
 689                 goto done;
 690
 691         for (;;) {
 692                 if (cancel_cb) {
 693                         err = (*cancel_cb)(cancel_arg);
 694                         if (err)
 695                                 break;
 696                 }
 697
 698                 if (!completed) {
 699                         err = find_yca_add_id(yca_id, graph, commit_ids, repo,
 700                             cancel_cb, cancel_arg);
 701                         if (err) {
 702                                 if (err->code != GOT_ERR_ITER_COMPLETED)
 703                                         break;
 704                                 err = NULL;
 705                                 completed = 1;
 706                         }
 707                         if (*yca_id)
 708                                 break;
 709                 }
 710
 711                 if (!completed2) {
 712                         err = find_yca_add_id(yca_id, graph2, commit_ids, repo,
 713                             cancel_cb, cancel_arg);
 714                         if (err) {
 715                                 if (err->code != GOT_ERR_ITER_COMPLETED)
 716                                         break;
 717                                 err = NULL;
 718                                 completed2 = 1;
 719                         }
 720                         if (*yca_id)
 721                                 break;
 722                 }
 723
 724                 if (completed && completed2) {
 725                         err = got_error(GOT_ERR_ANCESTRY);
 726                         break;
 727                 }
 728         }
 729 done:
 730         got_object_idset_free(commit_ids);
 731         if (graph)
 732                 got_commit_graph_close(graph);
 733         if (graph2)
 734                 got_commit_graph_close(graph2);
 735         return err;
 736 }