notes-merge.c

   1 #include "git-compat-util.h"
   2 #include "advice.h"
   3 #include "commit.h"
   4 #include "gettext.h"
   5 #include "refs.h"
   6 #include "object-file.h"
   7 #include "object-name.h"
   8 #include "object-store-ll.h"
   9 #include "path.h"
  10 #include "repository.h"
  11 #include "diff.h"
  12 #include "diffcore.h"
  13 #include "hex.h"
  14 #include "xdiff-interface.h"
  15 #include "merge-ll.h"
  16 #include "dir.h"
  17 #include "notes.h"
  18 #include "notes-merge.h"
  19 #include "strbuf.h"
  20 #include "trace.h"
  21 #include "notes-utils.h"
  22 #include "commit-reach.h"
  23 #include "wrapper.h"
  24
  25 struct notes_merge_pair {
  26         struct object_id obj, base, local, remote;
  27 };
  28
  29 void init_notes_merge_options(struct repository *r,
  30                               struct notes_merge_options *o)
  31 {
  32         memset(o, 0, sizeof(struct notes_merge_options));
  33         strbuf_init(&(o->commit_msg), 0);
  34         o->verbosity = NOTES_MERGE_VERBOSITY_DEFAULT;
  35         o->repo = r;
  36 }
  37
  38 static int path_to_oid(const char *path, struct object_id *oid)
  39 {
  40         char hex_oid[GIT_MAX_HEXSZ];
  41         int i = 0;
  42         while (*path && i < the_hash_algo->hexsz) {
  43                 if (*path != '/')
  44                         hex_oid[i++] = *path;
  45                 path++;
  46         }
  47         if (*path || i != the_hash_algo->hexsz)
  48                 return -1;
  49         return get_oid_hex(hex_oid, oid);
  50 }
  51
  52 static int verify_notes_filepair(struct diff_filepair *p, struct object_id *oid)
  53 {
  54         switch (p->status) {
  55         case DIFF_STATUS_MODIFIED:
  56                 assert(p->one->mode == p->two->mode);
  57                 assert(!is_null_oid(&p->one->oid));
  58                 assert(!is_null_oid(&p->two->oid));
  59                 break;
  60         case DIFF_STATUS_ADDED:
  61                 assert(is_null_oid(&p->one->oid));
  62                 break;
  63         case DIFF_STATUS_DELETED:
  64                 assert(is_null_oid(&p->two->oid));
  65                 break;
  66         default:
  67                 return -1;
  68         }
  69         assert(!strcmp(p->one->path, p->two->path));
  70         return path_to_oid(p->one->path, oid);
  71 }
  72
  73 static struct notes_merge_pair *find_notes_merge_pair_pos(
  74                 struct notes_merge_pair *list, int len, struct object_id *obj,
  75                 int insert_new, int *occupied)
  76 {
  77         /*
  78          * Both diff_tree_remote() and diff_tree_local() tend to process
  79          * merge_pairs in ascending order. Therefore, cache last returned
  80          * index, and search sequentially from there until the appropriate
  81          * position is found.
  82          *
  83          * Since inserts only happen from diff_tree_remote() (which mainly
  84          * _appends_), we don't care that inserting into the middle of the
  85          * list is expensive (using memmove()).
  86          */
  87         static int last_index;
  88         int i = last_index < len ? last_index : len - 1;
  89         int prev_cmp = 0, cmp = -1;
  90         while (i >= 0 && i < len) {
  91                 cmp = oidcmp(obj, &list[i].obj);
  92                 if (!cmp) /* obj belongs @ i */
  93                         break;
  94                 else if (cmp < 0 && prev_cmp <= 0) /* obj belongs < i */
  95                         i--;
  96                 else if (cmp < 0) /* obj belongs between i-1 and i */
  97                         break;
  98                 else if (cmp > 0 && prev_cmp >= 0) /* obj belongs > i */
  99                         i++;
 100                 else /* if (cmp > 0) */ { /* obj belongs between i and i+1 */
 101                         i++;
 102                         break;
 103                 }
 104                 prev_cmp = cmp;
 105         }
 106         if (i < 0)
 107                 i = 0;
 108         /* obj belongs at, or immediately preceding, index i (0 <= i <= len) */
 109
 110         if (!cmp)
 111                 *occupied = 1;
 112         else {
 113                 *occupied = 0;
 114                 if (insert_new && i < len) {
 115                         MOVE_ARRAY(list + i + 1, list + i, len - i);
 116                         memset(list + i, 0, sizeof(struct notes_merge_pair));
 117                 }
 118         }
 119         last_index = i;
 120         return list + i;
 121 }
 122
 123 static struct object_id uninitialized = {
 124         .hash =
 125         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
 126         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
 127 };
 128
 129 static struct notes_merge_pair *diff_tree_remote(struct notes_merge_options *o,
 130                                                  const struct object_id *base,
 131                                                  const struct object_id *remote,
 132                                                  int *num_changes)
 133 {
 134         struct diff_options opt;
 135         struct notes_merge_pair *changes;
 136         int i, len = 0;
 137
 138         trace_printf("\tdiff_tree_remote(base = %.7s, remote = %.7s)\n",
 139                oid_to_hex(base), oid_to_hex(remote));
 140
 141         repo_diff_setup(o->repo, &opt);
 142         opt.flags.recursive = 1;
 143         opt.output_format = DIFF_FORMAT_NO_OUTPUT;
 144         diff_setup_done(&opt);
 145         diff_tree_oid(base, remote, "", &opt);
 146         diffcore_std(&opt);
 147
 148         CALLOC_ARRAY(changes, diff_queued_diff.nr);
 149
 150         for (i = 0; i < diff_queued_diff.nr; i++) {
 151                 struct diff_filepair *p = diff_queued_diff.queue[i];
 152                 struct notes_merge_pair *mp;
 153                 int occupied;
 154                 struct object_id obj;
 155
 156                 if (verify_notes_filepair(p, &obj)) {
 157                         trace_printf("\t\tCannot merge entry '%s' (%c): "
 158                                "%.7s -> %.7s. Skipping!\n", p->one->path,
 159                                p->status, oid_to_hex(&p->one->oid),
 160                                oid_to_hex(&p->two->oid));
 161                         continue;
 162                 }
 163                 mp = find_notes_merge_pair_pos(changes, len, &obj, 1, &occupied);
 164                 if (occupied) {
 165                         /* We've found an addition/deletion pair */
 166                         assert(oideq(&mp->obj, &obj));
 167                         if (is_null_oid(&p->one->oid)) { /* addition */
 168                                 assert(is_null_oid(&mp->remote));
 169                                 oidcpy(&mp->remote, &p->two->oid);
 170                         } else if (is_null_oid(&p->two->oid)) { /* deletion */
 171                                 assert(is_null_oid(&mp->base));
 172                                 oidcpy(&mp->base, &p->one->oid);
 173                         } else
 174                                 assert(!"Invalid existing change recorded");
 175                 } else {
 176                         oidcpy(&mp->obj, &obj);
 177                         oidcpy(&mp->base, &p->one->oid);
 178                         oidcpy(&mp->local, &uninitialized);
 179                         oidcpy(&mp->remote, &p->two->oid);
 180                         len++;
 181                 }
 182                 trace_printf("\t\tStored remote change for %s: %.7s -> %.7s\n",
 183                        oid_to_hex(&mp->obj), oid_to_hex(&mp->base),
 184                        oid_to_hex(&mp->remote));
 185         }
 186         diff_flush(&opt);
 187
 188         *num_changes = len;
 189         return changes;
 190 }
 191
 192 static void diff_tree_local(struct notes_merge_options *o,
 193                             struct notes_merge_pair *changes, int len,
 194                             const struct object_id *base,
 195                             const struct object_id *local)
 196 {
 197         struct diff_options opt;
 198         int i;
 199
 200         trace_printf("\tdiff_tree_local(len = %i, base = %.7s, local = %.7s)\n",
 201                len, oid_to_hex(base), oid_to_hex(local));
 202
 203         repo_diff_setup(o->repo, &opt);
 204         opt.flags.recursive = 1;
 205         opt.output_format = DIFF_FORMAT_NO_OUTPUT;
 206         diff_setup_done(&opt);
 207         diff_tree_oid(base, local, "", &opt);
 208         diffcore_std(&opt);
 209
 210         for (i = 0; i < diff_queued_diff.nr; i++) {
 211                 struct diff_filepair *p = diff_queued_diff.queue[i];
 212                 struct notes_merge_pair *mp;
 213                 int match;
 214                 struct object_id obj;
 215
 216                 if (verify_notes_filepair(p, &obj)) {
 217                         trace_printf("\t\tCannot merge entry '%s' (%c): "
 218                                "%.7s -> %.7s. Skipping!\n", p->one->path,
 219                                p->status, oid_to_hex(&p->one->oid),
 220                                oid_to_hex(&p->two->oid));
 221                         continue;
 222                 }
 223                 mp = find_notes_merge_pair_pos(changes, len, &obj, 0, &match);
 224                 if (!match) {
 225                         trace_printf("\t\tIgnoring local-only change for %s: "
 226                                "%.7s -> %.7s\n", oid_to_hex(&obj),
 227                                oid_to_hex(&p->one->oid),
 228                                oid_to_hex(&p->two->oid));
 229                         continue;
 230                 }
 231
 232                 assert(oideq(&mp->obj, &obj));
 233                 if (is_null_oid(&p->two->oid)) { /* deletion */
 234                         /*
 235                          * Either this is a true deletion (1), or it is part
 236                          * of an A/D pair (2), or D/A pair (3):
 237                          *
 238                          * (1) mp->local is uninitialized; set it to null_sha1
 239                          * (2) mp->local is not uninitialized; don't touch it
 240                          * (3) mp->local is uninitialized; set it to null_sha1
 241                          *     (will be overwritten by following addition)
 242                          */
 243                         if (oideq(&mp->local, &uninitialized))
 244                                 oidclr(&mp->local);
 245                 } else if (is_null_oid(&p->one->oid)) { /* addition */
 246                         /*
 247                          * Either this is a true addition (1), or it is part
 248                          * of an A/D pair (2), or D/A pair (3):
 249                          *
 250                          * (1) mp->local is uninitialized; set to p->two->sha1
 251                          * (2) mp->local is uninitialized; set to p->two->sha1
 252                          * (3) mp->local is null_sha1;     set to p->two->sha1
 253                          */
 254                         assert(is_null_oid(&mp->local) ||
 255                                oideq(&mp->local, &uninitialized));
 256                         oidcpy(&mp->local, &p->two->oid);
 257                 } else { /* modification */
 258                         /*
 259                          * This is a true modification. p->one->sha1 shall
 260                          * match mp->base, and mp->local shall be uninitialized.
 261                          * Set mp->local to p->two->sha1.
 262                          */
 263                         assert(oideq(&p->one->oid, &mp->base));
 264                         assert(oideq(&mp->local, &uninitialized));
 265                         oidcpy(&mp->local, &p->two->oid);
 266                 }
 267                 trace_printf("\t\tStored local change for %s: %.7s -> %.7s\n",
 268                        oid_to_hex(&mp->obj), oid_to_hex(&mp->base),
 269                        oid_to_hex(&mp->local));
 270         }
 271         diff_flush(&opt);
 272 }
 273
 274 static void check_notes_merge_worktree(struct notes_merge_options *o)
 275 {
 276         if (!o->has_worktree) {
 277                 /*
 278                  * Must establish NOTES_MERGE_WORKTREE.
 279                  * Abort if NOTES_MERGE_WORKTREE already exists
 280                  */
 281                 if (file_exists(git_path(NOTES_MERGE_WORKTREE)) &&
 282                     !is_empty_dir(git_path(NOTES_MERGE_WORKTREE))) {
 283                         if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
 284                                 die(_("You have not concluded your previous "
 285                                     "notes merge (%s exists).\nPlease, use "
 286                                     "'git notes merge --commit' or 'git notes "
 287                                     "merge --abort' to commit/abort the "
 288                                     "previous merge before you start a new "
 289                                     "notes merge."), git_path("NOTES_MERGE_*"));
 290                         else
 291                                 die(_("You have not concluded your notes merge "
 292                                     "(%s exists)."), git_path("NOTES_MERGE_*"));
 293                 }
 294
 295                 if (safe_create_leading_directories_const(git_path(
 296                                 NOTES_MERGE_WORKTREE "/.test")))
 297                         die_errno("unable to create directory %s",
 298                                   git_path(NOTES_MERGE_WORKTREE));
 299                 o->has_worktree = 1;
 300         } else if (!file_exists(git_path(NOTES_MERGE_WORKTREE)))
 301                 /* NOTES_MERGE_WORKTREE should already be established */
 302                 die("missing '%s'. This should not happen",
 303                     git_path(NOTES_MERGE_WORKTREE));
 304 }
 305
 306 static void write_buf_to_worktree(const struct object_id *obj,
 307                                   const char *buf, unsigned long size)
 308 {
 309         int fd;
 310         char *path = git_pathdup(NOTES_MERGE_WORKTREE "/%s", oid_to_hex(obj));
 311         if (safe_create_leading_directories_const(path))
 312                 die_errno("unable to create directory for '%s'", path);
 313
 314         fd = xopen(path, O_WRONLY | O_EXCL | O_CREAT, 0666);
 315
 316         while (size > 0) {
 317                 ssize_t ret = write_in_full(fd, buf, size);
 318                 if (ret < 0) {
 319                         /* Ignore epipe */
 320                         if (errno == EPIPE)
 321                                 break;
 322                         die_errno("notes-merge");
 323                 }
 324                 size -= ret;
 325                 buf += ret;
 326         }
 327
 328         close(fd);
 329         free(path);
 330 }
 331
 332 static void write_note_to_worktree(const struct object_id *obj,
 333                                    const struct object_id *note)
 334 {
 335         enum object_type type;
 336         unsigned long size;
 337         void *buf = repo_read_object_file(the_repository, note, &type, &size);
 338
 339         if (!buf)
 340                 die("cannot read note %s for object %s",
 341                     oid_to_hex(note), oid_to_hex(obj));
 342         if (type != OBJ_BLOB)
 343                 die("blob expected in note %s for object %s",
 344                     oid_to_hex(note), oid_to_hex(obj));
 345         write_buf_to_worktree(obj, buf, size);
 346         free(buf);
 347 }
 348
 349 static int ll_merge_in_worktree(struct notes_merge_options *o,
 350                                 struct notes_merge_pair *p)
 351 {
 352         mmbuffer_t result_buf;
 353         mmfile_t base, local, remote;
 354         enum ll_merge_result status;
 355
 356         read_mmblob(&base, &p->base);
 357         read_mmblob(&local, &p->local);
 358         read_mmblob(&remote, &p->remote);
 359
 360         status = ll_merge(&result_buf, oid_to_hex(&p->obj), &base, NULL,
 361                           &local, o->local_ref, &remote, o->remote_ref,
 362                           o->repo->index, NULL);
 363
 364         free(base.ptr);
 365         free(local.ptr);
 366         free(remote.ptr);
 367
 368         if (status == LL_MERGE_BINARY_CONFLICT)
 369                 warning("Cannot merge binary files: %s (%s vs. %s)",
 370                         oid_to_hex(&p->obj), o->local_ref, o->remote_ref);
 371         if ((status < 0) || !result_buf.ptr)
 372                 die("Failed to execute internal merge");
 373
 374         write_buf_to_worktree(&p->obj, result_buf.ptr, result_buf.size);
 375         free(result_buf.ptr);
 376
 377         return status;
 378 }
 379
 380 static int merge_one_change_manual(struct notes_merge_options *o,
 381                                    struct notes_merge_pair *p,
 382                                    struct notes_tree *t)
 383 {
 384         const char *lref = o->local_ref ? o->local_ref : "local version";
 385         const char *rref = o->remote_ref ? o->remote_ref : "remote version";
 386
 387         trace_printf("\t\t\tmerge_one_change_manual(obj = %.7s, base = %.7s, "
 388                "local = %.7s, remote = %.7s)\n",
 389                oid_to_hex(&p->obj), oid_to_hex(&p->base),
 390                oid_to_hex(&p->local), oid_to_hex(&p->remote));
 391
 392         /* add "Conflicts:" section to commit message first time through */
 393         if (!o->has_worktree)
 394                 strbuf_addstr(&(o->commit_msg), "\n\nConflicts:\n");
 395
 396         strbuf_addf(&(o->commit_msg), "\t%s\n", oid_to_hex(&p->obj));
 397
 398         if (o->verbosity >= 2)
 399                 printf("Auto-merging notes for %s\n", oid_to_hex(&p->obj));
 400         check_notes_merge_worktree(o);
 401         if (is_null_oid(&p->local)) {
 402                 /* D/F conflict, checkout p->remote */
 403                 assert(!is_null_oid(&p->remote));
 404                 if (o->verbosity >= 1)
 405                         printf("CONFLICT (delete/modify): Notes for object %s "
 406                                 "deleted in %s and modified in %s. Version from %s "
 407                                 "left in tree.\n",
 408                                 oid_to_hex(&p->obj), lref, rref, rref);
 409                 write_note_to_worktree(&p->obj, &p->remote);
 410         } else if (is_null_oid(&p->remote)) {
 411                 /* D/F conflict, checkout p->local */
 412                 assert(!is_null_oid(&p->local));
 413                 if (o->verbosity >= 1)
 414                         printf("CONFLICT (delete/modify): Notes for object %s "
 415                                 "deleted in %s and modified in %s. Version from %s "
 416                                 "left in tree.\n",
 417                                 oid_to_hex(&p->obj), rref, lref, lref);
 418                 write_note_to_worktree(&p->obj, &p->local);
 419         } else {
 420                 /* "regular" conflict, checkout result of ll_merge() */
 421                 const char *reason = "content";
 422                 if (is_null_oid(&p->base))
 423                         reason = "add/add";
 424                 assert(!is_null_oid(&p->local));
 425                 assert(!is_null_oid(&p->remote));
 426                 if (o->verbosity >= 1)
 427                         printf("CONFLICT (%s): Merge conflict in notes for "
 428                                 "object %s\n", reason,
 429                                 oid_to_hex(&p->obj));
 430                 ll_merge_in_worktree(o, p);
 431         }
 432
 433         trace_printf("\t\t\tremoving from partial merge result\n");
 434         remove_note(t, p->obj.hash);
 435
 436         return 1;
 437 }
 438
 439 static int merge_one_change(struct notes_merge_options *o,
 440                             struct notes_merge_pair *p, struct notes_tree *t)
 441 {
 442         /*
 443          * Return 0 if change is successfully resolved (stored in notes_tree).
 444          * Return 1 is change results in a conflict (NOT stored in notes_tree,
 445          * but instead written to NOTES_MERGE_WORKTREE with conflict markers).
 446          */
 447         switch (o->strategy) {
 448         case NOTES_MERGE_RESOLVE_MANUAL:
 449                 return merge_one_change_manual(o, p, t);
 450         case NOTES_MERGE_RESOLVE_OURS:
 451                 if (o->verbosity >= 2)
 452                         printf("Using local notes for %s\n",
 453                                                 oid_to_hex(&p->obj));
 454                 /* nothing to do */
 455                 return 0;
 456         case NOTES_MERGE_RESOLVE_THEIRS:
 457                 if (o->verbosity >= 2)
 458                         printf("Using remote notes for %s\n",
 459                                                 oid_to_hex(&p->obj));
 460                 if (add_note(t, &p->obj, &p->remote, combine_notes_overwrite))
 461                         BUG("combine_notes_overwrite failed");
 462                 return 0;
 463         case NOTES_MERGE_RESOLVE_UNION:
 464                 if (o->verbosity >= 2)
 465                         printf("Concatenating local and remote notes for %s\n",
 466                                                         oid_to_hex(&p->obj));
 467                 if (add_note(t, &p->obj, &p->remote, combine_notes_concatenate))
 468                         die("failed to concatenate notes "
 469                             "(combine_notes_concatenate)");
 470                 return 0;
 471         case NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ:
 472                 if (o->verbosity >= 2)
 473                         printf("Concatenating unique lines in local and remote "
 474                                 "notes for %s\n", oid_to_hex(&p->obj));
 475                 if (add_note(t, &p->obj, &p->remote, combine_notes_cat_sort_uniq))
 476                         die("failed to concatenate notes "
 477                             "(combine_notes_cat_sort_uniq)");
 478                 return 0;
 479         }
 480         die("Unknown strategy (%i).", o->strategy);
 481 }
 482
 483 static int merge_changes(struct notes_merge_options *o,
 484                          struct notes_merge_pair *changes, int *num_changes,
 485                          struct notes_tree *t)
 486 {
 487         int i, conflicts = 0;
 488
 489         trace_printf("\tmerge_changes(num_changes = %i)\n", *num_changes);
 490         for (i = 0; i < *num_changes; i++) {
 491                 struct notes_merge_pair *p = changes + i;
 492                 trace_printf("\t\t%.7s: %.7s -> %.7s/%.7s\n",
 493                        oid_to_hex(&p->obj), oid_to_hex(&p->base),
 494                        oid_to_hex(&p->local),
 495                        oid_to_hex(&p->remote));
 496
 497                 if (oideq(&p->base, &p->remote)) {
 498                         /* no remote change; nothing to do */
 499                         trace_printf("\t\t\tskipping (no remote change)\n");
 500                 } else if (oideq(&p->local, &p->remote)) {
 501                         /* same change in local and remote; nothing to do */
 502                         trace_printf("\t\t\tskipping (local == remote)\n");
 503                 } else if (oideq(&p->local, &uninitialized) ||
 504                            oideq(&p->local, &p->base)) {
 505                         /* no local change; adopt remote change */
 506                         trace_printf("\t\t\tno local change, adopted remote\n");
 507                         if (add_note(t, &p->obj, &p->remote,
 508                                      combine_notes_overwrite))
 509                                 BUG("combine_notes_overwrite failed");
 510                 } else {
 511                         /* need file-level merge between local and remote */
 512                         trace_printf("\t\t\tneed content-level merge\n");
 513                         conflicts += merge_one_change(o, p, t);
 514                 }
 515         }
 516
 517         return conflicts;
 518 }
 519
 520 static int merge_from_diffs(struct notes_merge_options *o,
 521                             const struct object_id *base,
 522                             const struct object_id *local,
 523                             const struct object_id *remote,
 524                             struct notes_tree *t)
 525 {
 526         struct notes_merge_pair *changes;
 527         int num_changes, conflicts;
 528
 529         trace_printf("\tmerge_from_diffs(base = %.7s, local = %.7s, "
 530                "remote = %.7s)\n", oid_to_hex(base), oid_to_hex(local),
 531                oid_to_hex(remote));
 532
 533         changes = diff_tree_remote(o, base, remote, &num_changes);
 534         diff_tree_local(o, changes, num_changes, base, local);
 535
 536         conflicts = merge_changes(o, changes, &num_changes, t);
 537         free(changes);
 538
 539         if (o->verbosity >= 4)
 540                 printf(t->dirty ?
 541                        "Merge result: %i unmerged notes and a dirty notes tree\n" :
 542                        "Merge result: %i unmerged notes and a clean notes tree\n",
 543                        conflicts);
 544
 545         return conflicts ? -1 : 1;
 546 }
 547
 548 int notes_merge(struct notes_merge_options *o,
 549                 struct notes_tree *local_tree,
 550                 struct object_id *result_oid)
 551 {
 552         struct object_id local_oid, remote_oid;
 553         struct commit *local, *remote;
 554         struct commit_list *bases = NULL;
 555         const struct object_id *base_oid, *base_tree_oid;
 556         int result = 0;
 557
 558         assert(o->local_ref && o->remote_ref);
 559         assert(!strcmp(o->local_ref, local_tree->ref));
 560         oidclr(result_oid);
 561
 562         trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
 563                o->local_ref, o->remote_ref);
 564
 565         /* Dereference o->local_ref into local_sha1 */
 566         if (read_ref_full(o->local_ref, 0, &local_oid, NULL))
 567                 die("Failed to resolve local notes ref '%s'", o->local_ref);
 568         else if (!check_refname_format(o->local_ref, 0) &&
 569                 is_null_oid(&local_oid))
 570                 local = NULL; /* local_oid == null_oid indicates unborn ref */
 571         else if (!(local = lookup_commit_reference(o->repo, &local_oid)))
 572                 die("Could not parse local commit %s (%s)",
 573                     oid_to_hex(&local_oid), o->local_ref);
 574         trace_printf("\tlocal commit: %.7s\n", oid_to_hex(&local_oid));
 575
 576         /* Dereference o->remote_ref into remote_oid */
 577         if (repo_get_oid(the_repository, o->remote_ref, &remote_oid)) {
 578                 /*
 579                  * Failed to get remote_oid. If o->remote_ref looks like an
 580                  * unborn ref, perform the merge using an empty notes tree.
 581                  */
 582                 if (!check_refname_format(o->remote_ref, 0)) {
 583                         oidclr(&remote_oid);
 584                         remote = NULL;
 585                 } else {
 586                         die("Failed to resolve remote notes ref '%s'",
 587                             o->remote_ref);
 588                 }
 589         } else if (!(remote = lookup_commit_reference(o->repo, &remote_oid))) {
 590                 die("Could not parse remote commit %s (%s)",
 591                     oid_to_hex(&remote_oid), o->remote_ref);
 592         }
 593         trace_printf("\tremote commit: %.7s\n", oid_to_hex(&remote_oid));
 594
 595         if (!local && !remote)
 596                 die("Cannot merge empty notes ref (%s) into empty notes ref "
 597                     "(%s)", o->remote_ref, o->local_ref);
 598         if (!local) {
 599                 /* result == remote commit */
 600                 oidcpy(result_oid, &remote_oid);
 601                 goto found_result;
 602         }
 603         if (!remote) {
 604                 /* result == local commit */
 605                 oidcpy(result_oid, &local_oid);
 606                 goto found_result;
 607         }
 608         assert(local && remote);
 609
 610         /* Find merge bases */
 611         bases = repo_get_merge_bases(the_repository, local, remote);
 612         if (!bases) {
 613                 base_oid = null_oid();
 614                 base_tree_oid = the_hash_algo->empty_tree;
 615                 if (o->verbosity >= 4)
 616                         printf("No merge base found; doing history-less merge\n");
 617         } else if (!bases->next) {
 618                 base_oid = &bases->item->object.oid;
 619                 base_tree_oid = get_commit_tree_oid(bases->item);
 620                 if (o->verbosity >= 4)
 621                         printf("One merge base found (%.7s)\n",
 622                                oid_to_hex(base_oid));
 623         } else {
 624                 /* TODO: How to handle multiple merge-bases? */
 625                 base_oid = &bases->item->object.oid;
 626                 base_tree_oid = get_commit_tree_oid(bases->item);
 627                 if (o->verbosity >= 3)
 628                         printf("Multiple merge bases found. Using the first "
 629                                 "(%.7s)\n", oid_to_hex(base_oid));
 630         }
 631
 632         if (o->verbosity >= 4)
 633                 printf("Merging remote commit %.7s into local commit %.7s with "
 634                         "merge-base %.7s\n", oid_to_hex(&remote->object.oid),
 635                         oid_to_hex(&local->object.oid),
 636                         oid_to_hex(base_oid));
 637
 638         if (oideq(&remote->object.oid, base_oid)) {
 639                 /* Already merged; result == local commit */
 640                 if (o->verbosity >= 2)
 641                         printf_ln("Already up to date.");
 642                 oidcpy(result_oid, &local->object.oid);
 643                 goto found_result;
 644         }
 645         if (oideq(&local->object.oid, base_oid)) {
 646                 /* Fast-forward; result == remote commit */
 647                 if (o->verbosity >= 2)
 648                         printf("Fast-forward\n");
 649                 oidcpy(result_oid, &remote->object.oid);
 650                 goto found_result;
 651         }
 652
 653         result = merge_from_diffs(o, base_tree_oid,
 654                                   get_commit_tree_oid(local),
 655                                   get_commit_tree_oid(remote), local_tree);
 656
 657         if (result != 0) { /* non-trivial merge (with or without conflicts) */
 658                 /* Commit (partial) result */
 659                 struct commit_list *parents = NULL;
 660                 commit_list_insert(remote, &parents); /* LIFO order */
 661                 commit_list_insert(local, &parents);
 662                 create_notes_commit(o->repo, local_tree, parents, o->commit_msg.buf,
 663                                     o->commit_msg.len, result_oid);
 664         }
 665
 666 found_result:
 667         free_commit_list(bases);
 668         strbuf_release(&(o->commit_msg));
 669         trace_printf("notes_merge(): result = %i, result_oid = %.7s\n",
 670                result, oid_to_hex(result_oid));
 671         return result;
 672 }
 673
 674 int notes_merge_commit(struct notes_merge_options *o,
 675                        struct notes_tree *partial_tree,
 676                        struct commit *partial_commit,
 677                        struct object_id *result_oid)
 678 {
 679         /*
 680          * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
 681          * found notes to 'partial_tree'. Write the updated notes tree to
 682          * the DB, and commit the resulting tree object while reusing the
 683          * commit message and parents from 'partial_commit'.
 684          * Finally store the new commit object OID into 'result_oid'.
 685          */
 686         DIR *dir;
 687         struct dirent *e;
 688         struct strbuf path = STRBUF_INIT;
 689         const char *buffer = repo_get_commit_buffer(the_repository,
 690                                                     partial_commit, NULL);
 691         const char *msg = strstr(buffer, "\n\n");
 692         int baselen;
 693
 694         git_path_buf(&path, NOTES_MERGE_WORKTREE);
 695         if (o->verbosity >= 3)
 696                 printf("Committing notes in notes merge worktree at %s\n",
 697                         path.buf);
 698
 699         if (!msg || msg[2] == '\0')
 700                 die("partial notes commit has empty message");
 701         msg += 2;
 702
 703         dir = opendir(path.buf);
 704         if (!dir)
 705                 die_errno("could not open %s", path.buf);
 706
 707         strbuf_addch(&path, '/');
 708         baselen = path.len;
 709         while ((e = readdir_skip_dot_and_dotdot(dir)) != NULL) {
 710                 struct stat st;
 711                 struct object_id obj_oid, blob_oid;
 712
 713                 if (get_oid_hex(e->d_name, &obj_oid)) {
 714                         if (o->verbosity >= 3)
 715                                 printf("Skipping non-SHA1 entry '%s%s'\n",
 716                                         path.buf, e->d_name);
 717                         continue;
 718                 }
 719
 720                 strbuf_addstr(&path, e->d_name);
 721                 /* write file as blob, and add to partial_tree */
 722                 if (stat(path.buf, &st))
 723                         die_errno("Failed to stat '%s'", path.buf);
 724                 if (index_path(o->repo->index, &blob_oid, path.buf, &st, HASH_WRITE_OBJECT))
 725                         die("Failed to write blob object from '%s'", path.buf);
 726                 if (add_note(partial_tree, &obj_oid, &blob_oid, NULL))
 727                         die("Failed to add resolved note '%s' to notes tree",
 728                             path.buf);
 729                 if (o->verbosity >= 4)
 730                         printf("Added resolved note for object %s: %s\n",
 731                                 oid_to_hex(&obj_oid), oid_to_hex(&blob_oid));
 732                 strbuf_setlen(&path, baselen);
 733         }
 734
 735         create_notes_commit(o->repo, partial_tree, partial_commit->parents, msg,
 736                             strlen(msg), result_oid);
 737         repo_unuse_commit_buffer(the_repository, partial_commit, buffer);
 738         if (o->verbosity >= 4)
 739                 printf("Finalized notes merge commit: %s\n",
 740                         oid_to_hex(result_oid));
 741         strbuf_release(&path);
 742         closedir(dir);
 743         return 0;
 744 }
 745
 746 int notes_merge_abort(struct notes_merge_options *o)
 747 {
 748         /*
 749          * Remove all files within .git/NOTES_MERGE_WORKTREE. We do not remove
 750          * the .git/NOTES_MERGE_WORKTREE directory itself, since it might be
 751          * the current working directory of the user.
 752          */
 753         struct strbuf buf = STRBUF_INIT;
 754         int ret;
 755
 756         git_path_buf(&buf, NOTES_MERGE_WORKTREE);
 757         if (o->verbosity >= 3)
 758                 printf("Removing notes merge worktree at %s/*\n", buf.buf);
 759         ret = remove_dir_recursively(&buf, REMOVE_DIR_KEEP_TOPLEVEL);
 760         strbuf_release(&buf);
 761         return ret;
 762 }