git.oblomov.eu Git - git/blob - notes-merge.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "refs.h"
   4 #include "diff.h"
   5 #include "diffcore.h"
   6 #include "xdiff-interface.h"
   7 #include "ll-merge.h"
   8 #include "dir.h"
   9 #include "notes.h"
  10 #include "notes-merge.h"
  11 #include "strbuf.h"
  12
  13 struct notes_merge_pair {
  14         unsigned char obj[20], base[20], local[20], remote[20];
  15 };
  16
  17 void init_notes_merge_options(struct notes_merge_options *o)
  18 {
  19         memset(o, 0, sizeof(struct notes_merge_options));
  20         strbuf_init(&(o->commit_msg), 0);
  21         o->verbosity = NOTES_MERGE_VERBOSITY_DEFAULT;
  22 }
  23
  24 #define OUTPUT(o, v, ...) \
  25         do { \
  26                 if ((o)->verbosity >= (v)) { \
  27                         printf(__VA_ARGS__); \
  28                         puts(""); \
  29                 } \
  30         } while (0)
  31
  32 static int path_to_sha1(const char *path, unsigned char *sha1)
  33 {
  34         char hex_sha1[40];
  35         int i = 0;
  36         while (*path && i < 40) {
  37                 if (*path != '/')
  38                         hex_sha1[i++] = *path;
  39                 path++;
  40         }
  41         if (*path || i != 40)
  42                 return -1;
  43         return get_sha1_hex(hex_sha1, sha1);
  44 }
  45
  46 static int verify_notes_filepair(struct diff_filepair *p, unsigned char *sha1)
  47 {
  48         switch (p->status) {
  49         case DIFF_STATUS_MODIFIED:
  50                 assert(p->one->mode == p->two->mode);
  51                 assert(!is_null_sha1(p->one->sha1));
  52                 assert(!is_null_sha1(p->two->sha1));
  53                 break;
  54         case DIFF_STATUS_ADDED:
  55                 assert(is_null_sha1(p->one->sha1));
  56                 break;
  57         case DIFF_STATUS_DELETED:
  58                 assert(is_null_sha1(p->two->sha1));
  59                 break;
  60         default:
  61                 return -1;
  62         }
  63         assert(!strcmp(p->one->path, p->two->path));
  64         return path_to_sha1(p->one->path, sha1);
  65 }
  66
  67 static struct notes_merge_pair *find_notes_merge_pair_pos(
  68                 struct notes_merge_pair *list, int len, unsigned char *obj,
  69                 int insert_new, int *occupied)
  70 {
  71         /*
  72          * Both diff_tree_remote() and diff_tree_local() tend to process
  73          * merge_pairs in ascending order. Therefore, cache last returned
  74          * index, and search sequentially from there until the appropriate
  75          * position is found.
  76          *
  77          * Since inserts only happen from diff_tree_remote() (which mainly
  78          * _appends_), we don't care that inserting into the middle of the
  79          * list is expensive (using memmove()).
  80          */
  81         static int last_index;
  82         int i = last_index < len ? last_index : len - 1;
  83         int prev_cmp = 0, cmp = -1;
  84         while (i >= 0 && i < len) {
  85                 cmp = hashcmp(obj, list[i].obj);
  86                 if (!cmp) /* obj belongs @ i */
  87                         break;
  88                 else if (cmp < 0 && prev_cmp <= 0) /* obj belongs < i */
  89                         i--;
  90                 else if (cmp < 0) /* obj belongs between i-1 and i */
  91                         break;
  92                 else if (cmp > 0 && prev_cmp >= 0) /* obj belongs > i */
  93                         i++;
  94                 else /* if (cmp > 0) */ { /* obj belongs between i and i+1 */
  95                         i++;
  96                         break;
  97                 }
  98                 prev_cmp = cmp;
  99         }
 100         if (i < 0)
 101                 i = 0;
 102         /* obj belongs at, or immediately preceding, index i (0 <= i <= len) */
 103
 104         if (!cmp)
 105                 *occupied = 1;
 106         else {
 107                 *occupied = 0;
 108                 if (insert_new && i < len) {
 109                         memmove(list + i + 1, list + i,
 110                                 (len - i) * sizeof(struct notes_merge_pair));
 111                         memset(list + i, 0, sizeof(struct notes_merge_pair));
 112                 }
 113         }
 114         last_index = i;
 115         return list + i;
 116 }
 117
 118 static unsigned char uninitialized[20] =
 119         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
 120         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff";
 121
 122 static struct notes_merge_pair *diff_tree_remote(struct notes_merge_options *o,
 123                                                  const unsigned char *base,
 124                                                  const unsigned char *remote,
 125                                                  int *num_changes)
 126 {
 127         struct diff_options opt;
 128         struct notes_merge_pair *changes;
 129         int i, len = 0;
 130
 131         trace_printf("\tdiff_tree_remote(base = %.7s, remote = %.7s)\n",
 132                sha1_to_hex(base), sha1_to_hex(remote));
 133
 134         diff_setup(&opt);
 135         DIFF_OPT_SET(&opt, RECURSIVE);
 136         opt.output_format = DIFF_FORMAT_NO_OUTPUT;
 137         if (diff_setup_done(&opt) < 0)
 138                 die("diff_setup_done failed");
 139         diff_tree_sha1(base, remote, "", &opt);
 140         diffcore_std(&opt);
 141
 142         changes = xcalloc(diff_queued_diff.nr, sizeof(struct notes_merge_pair));
 143
 144         for (i = 0; i < diff_queued_diff.nr; i++) {
 145                 struct diff_filepair *p = diff_queued_diff.queue[i];
 146                 struct notes_merge_pair *mp;
 147                 int occupied;
 148                 unsigned char obj[20];
 149
 150                 if (verify_notes_filepair(p, obj)) {
 151                         trace_printf("\t\tCannot merge entry '%s' (%c): "
 152                                "%.7s -> %.7s. Skipping!\n", p->one->path,
 153                                p->status, sha1_to_hex(p->one->sha1),
 154                                sha1_to_hex(p->two->sha1));
 155                         continue;
 156                 }
 157                 mp = find_notes_merge_pair_pos(changes, len, obj, 1, &occupied);
 158                 if (occupied) {
 159                         /* We've found an addition/deletion pair */
 160                         assert(!hashcmp(mp->obj, obj));
 161                         if (is_null_sha1(p->one->sha1)) { /* addition */
 162                                 assert(is_null_sha1(mp->remote));
 163                                 hashcpy(mp->remote, p->two->sha1);
 164                         } else if (is_null_sha1(p->two->sha1)) { /* deletion */
 165                                 assert(is_null_sha1(mp->base));
 166                                 hashcpy(mp->base, p->one->sha1);
 167                         } else
 168                                 assert(!"Invalid existing change recorded");
 169                 } else {
 170                         hashcpy(mp->obj, obj);
 171                         hashcpy(mp->base, p->one->sha1);
 172                         hashcpy(mp->local, uninitialized);
 173                         hashcpy(mp->remote, p->two->sha1);
 174                         len++;
 175                 }
 176                 trace_printf("\t\tStored remote change for %s: %.7s -> %.7s\n",
 177                        sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
 178                        sha1_to_hex(mp->remote));
 179         }
 180         diff_flush(&opt);
 181         diff_tree_release_paths(&opt);
 182
 183         *num_changes = len;
 184         return changes;
 185 }
 186
 187 static void diff_tree_local(struct notes_merge_options *o,
 188                             struct notes_merge_pair *changes, int len,
 189                             const unsigned char *base,
 190                             const unsigned char *local)
 191 {
 192         struct diff_options opt;
 193         int i;
 194
 195         trace_printf("\tdiff_tree_local(len = %i, base = %.7s, local = %.7s)\n",
 196                len, sha1_to_hex(base), sha1_to_hex(local));
 197
 198         diff_setup(&opt);
 199         DIFF_OPT_SET(&opt, RECURSIVE);
 200         opt.output_format = DIFF_FORMAT_NO_OUTPUT;
 201         if (diff_setup_done(&opt) < 0)
 202                 die("diff_setup_done failed");
 203         diff_tree_sha1(base, local, "", &opt);
 204         diffcore_std(&opt);
 205
 206         for (i = 0; i < diff_queued_diff.nr; i++) {
 207                 struct diff_filepair *p = diff_queued_diff.queue[i];
 208                 struct notes_merge_pair *mp;
 209                 int match;
 210                 unsigned char obj[20];
 211
 212                 if (verify_notes_filepair(p, obj)) {
 213                         trace_printf("\t\tCannot merge entry '%s' (%c): "
 214                                "%.7s -> %.7s. Skipping!\n", p->one->path,
 215                                p->status, sha1_to_hex(p->one->sha1),
 216                                sha1_to_hex(p->two->sha1));
 217                         continue;
 218                 }
 219                 mp = find_notes_merge_pair_pos(changes, len, obj, 0, &match);
 220                 if (!match) {
 221                         trace_printf("\t\tIgnoring local-only change for %s: "
 222                                "%.7s -> %.7s\n", sha1_to_hex(obj),
 223                                sha1_to_hex(p->one->sha1),
 224                                sha1_to_hex(p->two->sha1));
 225                         continue;
 226                 }
 227
 228                 assert(!hashcmp(mp->obj, obj));
 229                 if (is_null_sha1(p->two->sha1)) { /* deletion */
 230                         /*
 231                          * Either this is a true deletion (1), or it is part
 232                          * of an A/D pair (2), or D/A pair (3):
 233                          *
 234                          * (1) mp->local is uninitialized; set it to null_sha1
 235                          * (2) mp->local is not uninitialized; don't touch it
 236                          * (3) mp->local is uninitialized; set it to null_sha1
 237                          *     (will be overwritten by following addition)
 238                          */
 239                         if (!hashcmp(mp->local, uninitialized))
 240                                 hashclr(mp->local);
 241                 } else if (is_null_sha1(p->one->sha1)) { /* addition */
 242                         /*
 243                          * Either this is a true addition (1), or it is part
 244                          * of an A/D pair (2), or D/A pair (3):
 245                          *
 246                          * (1) mp->local is uninitialized; set to p->two->sha1
 247                          * (2) mp->local is uninitialized; set to p->two->sha1
 248                          * (3) mp->local is null_sha1;     set to p->two->sha1
 249                          */
 250                         assert(is_null_sha1(mp->local) ||
 251                                !hashcmp(mp->local, uninitialized));
 252                         hashcpy(mp->local, p->two->sha1);
 253                 } else { /* modification */
 254                         /*
 255                          * This is a true modification. p->one->sha1 shall
 256                          * match mp->base, and mp->local shall be uninitialized.
 257                          * Set mp->local to p->two->sha1.
 258                          */
 259                         assert(!hashcmp(p->one->sha1, mp->base));
 260                         assert(!hashcmp(mp->local, uninitialized));
 261                         hashcpy(mp->local, p->two->sha1);
 262                 }
 263                 trace_printf("\t\tStored local change for %s: %.7s -> %.7s\n",
 264                        sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
 265                        sha1_to_hex(mp->local));
 266         }
 267         diff_flush(&opt);
 268         diff_tree_release_paths(&opt);
 269 }
 270
 271 static void check_notes_merge_worktree(struct notes_merge_options *o)
 272 {
 273         if (!o->has_worktree) {
 274                 /*
 275                  * Must establish NOTES_MERGE_WORKTREE.
 276                  * Abort if NOTES_MERGE_WORKTREE already exists
 277                  */
 278                 if (file_exists(git_path(NOTES_MERGE_WORKTREE))) {
 279                         if (advice_resolve_conflict)
 280                                 die("You have not concluded your previous "
 281                                     "notes merge (%s exists).\nPlease, use "
 282                                     "'git notes merge --commit' or 'git notes "
 283                                     "merge --abort' to commit/abort the "
 284                                     "previous merge before you start a new "
 285                                     "notes merge.", git_path("NOTES_MERGE_*"));
 286                         else
 287                                 die("You have not concluded your notes merge "
 288                                     "(%s exists).", git_path("NOTES_MERGE_*"));
 289                 }
 290
 291                 if (safe_create_leading_directories(git_path(
 292                                 NOTES_MERGE_WORKTREE "/.test")))
 293                         die_errno("unable to create directory %s",
 294                                   git_path(NOTES_MERGE_WORKTREE));
 295                 o->has_worktree = 1;
 296         } else if (!file_exists(git_path(NOTES_MERGE_WORKTREE)))
 297                 /* NOTES_MERGE_WORKTREE should already be established */
 298                 die("missing '%s'. This should not happen",
 299                     git_path(NOTES_MERGE_WORKTREE));
 300 }
 301
 302 static void write_buf_to_worktree(const unsigned char *obj,
 303                                   const char *buf, unsigned long size)
 304 {
 305         int fd;
 306         char *path = git_path(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
 307         if (safe_create_leading_directories(path))
 308                 die_errno("unable to create directory for '%s'", path);
 309         if (file_exists(path))
 310                 die("found existing file at '%s'", path);
 311
 312         fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, 0666);
 313         if (fd < 0)
 314                 die_errno("failed to open '%s'", path);
 315
 316         while (size > 0) {
 317                 long 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                 } else if (!ret) {
 324                         die("notes-merge: disk full?");
 325                 }
 326                 size -= ret;
 327                 buf += ret;
 328         }
 329
 330         close(fd);
 331 }
 332
 333 static void write_note_to_worktree(const unsigned char *obj,
 334                                    const unsigned char *note)
 335 {
 336         enum object_type type;
 337         unsigned long size;
 338         void *buf = read_sha1_file(note, &type, &size);
 339
 340         if (!buf)
 341                 die("cannot read note %s for object %s",
 342                     sha1_to_hex(note), sha1_to_hex(obj));
 343         if (type != OBJ_BLOB)
 344                 die("blob expected in note %s for object %s",
 345                     sha1_to_hex(note), sha1_to_hex(obj));
 346         write_buf_to_worktree(obj, buf, size);
 347         free(buf);
 348 }
 349
 350 static int ll_merge_in_worktree(struct notes_merge_options *o,
 351                                 struct notes_merge_pair *p)
 352 {
 353         mmbuffer_t result_buf;
 354         mmfile_t base, local, remote;
 355         int status;
 356
 357         read_mmblob(&base, p->base);
 358         read_mmblob(&local, p->local);
 359         read_mmblob(&remote, p->remote);
 360
 361         status = ll_merge(&result_buf, sha1_to_hex(p->obj), &base, NULL,
 362                           &local, o->local_ref, &remote, o->remote_ref, NULL);
 363
 364         free(base.ptr);
 365         free(local.ptr);
 366         free(remote.ptr);
 367
 368         if ((status < 0) || !result_buf.ptr)
 369                 die("Failed to execute internal merge");
 370
 371         write_buf_to_worktree(p->obj, result_buf.ptr, result_buf.size);
 372         free(result_buf.ptr);
 373
 374         return status;
 375 }
 376
 377 static int merge_one_change_manual(struct notes_merge_options *o,
 378                                    struct notes_merge_pair *p,
 379                                    struct notes_tree *t)
 380 {
 381         const char *lref = o->local_ref ? o->local_ref : "local version";
 382         const char *rref = o->remote_ref ? o->remote_ref : "remote version";
 383
 384         trace_printf("\t\t\tmerge_one_change_manual(obj = %.7s, base = %.7s, "
 385                "local = %.7s, remote = %.7s)\n",
 386                sha1_to_hex(p->obj), sha1_to_hex(p->base),
 387                sha1_to_hex(p->local), sha1_to_hex(p->remote));
 388
 389         /* add "Conflicts:" section to commit message first time through */
 390         if (!o->has_worktree)
 391                 strbuf_addstr(&(o->commit_msg), "\n\nConflicts:\n");
 392
 393         strbuf_addf(&(o->commit_msg), "\t%s\n", sha1_to_hex(p->obj));
 394
 395         OUTPUT(o, 2, "Auto-merging notes for %s", sha1_to_hex(p->obj));
 396         check_notes_merge_worktree(o);
 397         if (is_null_sha1(p->local)) {
 398                 /* D/F conflict, checkout p->remote */
 399                 assert(!is_null_sha1(p->remote));
 400                 OUTPUT(o, 1, "CONFLICT (delete/modify): Notes for object %s "
 401                        "deleted in %s and modified in %s. Version from %s "
 402                        "left in tree.", sha1_to_hex(p->obj), lref, rref, rref);
 403                 write_note_to_worktree(p->obj, p->remote);
 404         } else if (is_null_sha1(p->remote)) {
 405                 /* D/F conflict, checkout p->local */
 406                 assert(!is_null_sha1(p->local));
 407                 OUTPUT(o, 1, "CONFLICT (delete/modify): Notes for object %s "
 408                        "deleted in %s and modified in %s. Version from %s "
 409                        "left in tree.", sha1_to_hex(p->obj), rref, lref, lref);
 410                 write_note_to_worktree(p->obj, p->local);
 411         } else {
 412                 /* "regular" conflict, checkout result of ll_merge() */
 413                 const char *reason = "content";
 414                 if (is_null_sha1(p->base))
 415                         reason = "add/add";
 416                 assert(!is_null_sha1(p->local));
 417                 assert(!is_null_sha1(p->remote));
 418                 OUTPUT(o, 1, "CONFLICT (%s): Merge conflict in notes for "
 419                        "object %s", reason, sha1_to_hex(p->obj));
 420                 ll_merge_in_worktree(o, p);
 421         }
 422
 423         trace_printf("\t\t\tremoving from partial merge result\n");
 424         remove_note(t, p->obj);
 425
 426         return 1;
 427 }
 428
 429 static int merge_one_change(struct notes_merge_options *o,
 430                             struct notes_merge_pair *p, struct notes_tree *t)
 431 {
 432         /*
 433          * Return 0 if change is successfully resolved (stored in notes_tree).
 434          * Return 1 is change results in a conflict (NOT stored in notes_tree,
 435          * but instead written to NOTES_MERGE_WORKTREE with conflict markers).
 436          */
 437         switch (o->strategy) {
 438         case NOTES_MERGE_RESOLVE_MANUAL:
 439                 return merge_one_change_manual(o, p, t);
 440         case NOTES_MERGE_RESOLVE_OURS:
 441                 OUTPUT(o, 2, "Using local notes for %s", sha1_to_hex(p->obj));
 442                 /* nothing to do */
 443                 return 0;
 444         case NOTES_MERGE_RESOLVE_THEIRS:
 445                 OUTPUT(o, 2, "Using remote notes for %s", sha1_to_hex(p->obj));
 446                 if (add_note(t, p->obj, p->remote, combine_notes_overwrite))
 447                         die("BUG: combine_notes_overwrite failed");
 448                 return 0;
 449         case NOTES_MERGE_RESOLVE_UNION:
 450                 OUTPUT(o, 2, "Concatenating local and remote notes for %s",
 451                        sha1_to_hex(p->obj));
 452                 if (add_note(t, p->obj, p->remote, combine_notes_concatenate))
 453                         die("failed to concatenate notes "
 454                             "(combine_notes_concatenate)");
 455                 return 0;
 456         case NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ:
 457                 OUTPUT(o, 2, "Concatenating unique lines in local and remote "
 458                        "notes for %s", sha1_to_hex(p->obj));
 459                 if (add_note(t, p->obj, p->remote, combine_notes_cat_sort_uniq))
 460                         die("failed to concatenate notes "
 461                             "(combine_notes_cat_sort_uniq)");
 462                 return 0;
 463         }
 464         die("Unknown strategy (%i).", o->strategy);
 465 }
 466
 467 static int merge_changes(struct notes_merge_options *o,
 468                          struct notes_merge_pair *changes, int *num_changes,
 469                          struct notes_tree *t)
 470 {
 471         int i, conflicts = 0;
 472
 473         trace_printf("\tmerge_changes(num_changes = %i)\n", *num_changes);
 474         for (i = 0; i < *num_changes; i++) {
 475                 struct notes_merge_pair *p = changes + i;
 476                 trace_printf("\t\t%.7s: %.7s -> %.7s/%.7s\n",
 477                        sha1_to_hex(p->obj), sha1_to_hex(p->base),
 478                        sha1_to_hex(p->local), sha1_to_hex(p->remote));
 479
 480                 if (!hashcmp(p->base, p->remote)) {
 481                         /* no remote change; nothing to do */
 482                         trace_printf("\t\t\tskipping (no remote change)\n");
 483                 } else if (!hashcmp(p->local, p->remote)) {
 484                         /* same change in local and remote; nothing to do */
 485                         trace_printf("\t\t\tskipping (local == remote)\n");
 486                 } else if (!hashcmp(p->local, uninitialized) ||
 487                            !hashcmp(p->local, p->base)) {
 488                         /* no local change; adopt remote change */
 489                         trace_printf("\t\t\tno local change, adopted remote\n");
 490                         if (add_note(t, p->obj, p->remote,
 491                                      combine_notes_overwrite))
 492                                 die("BUG: combine_notes_overwrite failed");
 493                 } else {
 494                         /* need file-level merge between local and remote */
 495                         trace_printf("\t\t\tneed content-level merge\n");
 496                         conflicts += merge_one_change(o, p, t);
 497                 }
 498         }
 499
 500         return conflicts;
 501 }
 502
 503 static int merge_from_diffs(struct notes_merge_options *o,
 504                             const unsigned char *base,
 505                             const unsigned char *local,
 506                             const unsigned char *remote, struct notes_tree *t)
 507 {
 508         struct notes_merge_pair *changes;
 509         int num_changes, conflicts;
 510
 511         trace_printf("\tmerge_from_diffs(base = %.7s, local = %.7s, "
 512                "remote = %.7s)\n", sha1_to_hex(base), sha1_to_hex(local),
 513                sha1_to_hex(remote));
 514
 515         changes = diff_tree_remote(o, base, remote, &num_changes);
 516         diff_tree_local(o, changes, num_changes, base, local);
 517
 518         conflicts = merge_changes(o, changes, &num_changes, t);
 519         free(changes);
 520
 521         OUTPUT(o, 4, "Merge result: %i unmerged notes and a %s notes tree",
 522                conflicts, t->dirty ? "dirty" : "clean");
 523
 524         return conflicts ? -1 : 1;
 525 }
 526
 527 void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 528                          const char *msg, unsigned char *result_sha1)
 529 {
 530         unsigned char tree_sha1[20];
 531
 532         assert(t->initialized);
 533
 534         if (write_notes_tree(t, tree_sha1))
 535                 die("Failed to write notes tree to database");
 536
 537         if (!parents) {
 538                 /* Deduce parent commit from t->ref */
 539                 unsigned char parent_sha1[20];
 540                 if (!read_ref(t->ref, parent_sha1)) {
 541                         struct commit *parent = lookup_commit(parent_sha1);
 542                         if (!parent || parse_commit(parent))
 543                                 die("Failed to find/parse commit %s", t->ref);
 544                         commit_list_insert(parent, &parents);
 545                 }
 546                 /* else: t->ref points to nothing, assume root/orphan commit */
 547         }
 548
 549         if (commit_tree(msg, tree_sha1, parents, result_sha1, NULL))
 550                 die("Failed to commit notes tree to database");
 551 }
 552
 553 int notes_merge(struct notes_merge_options *o,
 554                 struct notes_tree *local_tree,
 555                 unsigned char *result_sha1)
 556 {
 557         unsigned char local_sha1[20], remote_sha1[20];
 558         struct commit *local, *remote;
 559         struct commit_list *bases = NULL;
 560         const unsigned char *base_sha1, *base_tree_sha1;
 561         int result = 0;
 562
 563         assert(o->local_ref && o->remote_ref);
 564         assert(!strcmp(o->local_ref, local_tree->ref));
 565         hashclr(result_sha1);
 566
 567         trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
 568                o->local_ref, o->remote_ref);
 569
 570         /* Dereference o->local_ref into local_sha1 */
 571         if (!resolve_ref(o->local_ref, local_sha1, 0, NULL))
 572                 die("Failed to resolve local notes ref '%s'", o->local_ref);
 573         else if (!check_ref_format(o->local_ref) && is_null_sha1(local_sha1))
 574                 local = NULL; /* local_sha1 == null_sha1 indicates unborn ref */
 575         else if (!(local = lookup_commit_reference(local_sha1)))
 576                 die("Could not parse local commit %s (%s)",
 577                     sha1_to_hex(local_sha1), o->local_ref);
 578         trace_printf("\tlocal commit: %.7s\n", sha1_to_hex(local_sha1));
 579
 580         /* Dereference o->remote_ref into remote_sha1 */
 581         if (get_sha1(o->remote_ref, remote_sha1)) {
 582                 /*
 583                  * Failed to get remote_sha1. If o->remote_ref looks like an
 584                  * unborn ref, perform the merge using an empty notes tree.
 585                  */
 586                 if (!check_ref_format(o->remote_ref)) {
 587                         hashclr(remote_sha1);
 588                         remote = NULL;
 589                 } else {
 590                         die("Failed to resolve remote notes ref '%s'",
 591                             o->remote_ref);
 592                 }
 593         } else if (!(remote = lookup_commit_reference(remote_sha1))) {
 594                 die("Could not parse remote commit %s (%s)",
 595                     sha1_to_hex(remote_sha1), o->remote_ref);
 596         }
 597         trace_printf("\tremote commit: %.7s\n", sha1_to_hex(remote_sha1));
 598
 599         if (!local && !remote)
 600                 die("Cannot merge empty notes ref (%s) into empty notes ref "
 601                     "(%s)", o->remote_ref, o->local_ref);
 602         if (!local) {
 603                 /* result == remote commit */
 604                 hashcpy(result_sha1, remote_sha1);
 605                 goto found_result;
 606         }
 607         if (!remote) {
 608                 /* result == local commit */
 609                 hashcpy(result_sha1, local_sha1);
 610                 goto found_result;
 611         }
 612         assert(local && remote);
 613
 614         /* Find merge bases */
 615         bases = get_merge_bases(local, remote, 1);
 616         if (!bases) {
 617                 base_sha1 = null_sha1;
 618                 base_tree_sha1 = EMPTY_TREE_SHA1_BIN;
 619                 OUTPUT(o, 4, "No merge base found; doing history-less merge");
 620         } else if (!bases->next) {
 621                 base_sha1 = bases->item->object.sha1;
 622                 base_tree_sha1 = bases->item->tree->object.sha1;
 623                 OUTPUT(o, 4, "One merge base found (%.7s)",
 624                        sha1_to_hex(base_sha1));
 625         } else {
 626                 /* TODO: How to handle multiple merge-bases? */
 627                 base_sha1 = bases->item->object.sha1;
 628                 base_tree_sha1 = bases->item->tree->object.sha1;
 629                 OUTPUT(o, 3, "Multiple merge bases found. Using the first "
 630                        "(%.7s)", sha1_to_hex(base_sha1));
 631         }
 632
 633         OUTPUT(o, 4, "Merging remote commit %.7s into local commit %.7s with "
 634                "merge-base %.7s", sha1_to_hex(remote->object.sha1),
 635                sha1_to_hex(local->object.sha1), sha1_to_hex(base_sha1));
 636
 637         if (!hashcmp(remote->object.sha1, base_sha1)) {
 638                 /* Already merged; result == local commit */
 639                 OUTPUT(o, 2, "Already up-to-date!");
 640                 hashcpy(result_sha1, local->object.sha1);
 641                 goto found_result;
 642         }
 643         if (!hashcmp(local->object.sha1, base_sha1)) {
 644                 /* Fast-forward; result == remote commit */
 645                 OUTPUT(o, 2, "Fast-forward");
 646                 hashcpy(result_sha1, remote->object.sha1);
 647                 goto found_result;
 648         }
 649
 650         result = merge_from_diffs(o, base_tree_sha1, local->tree->object.sha1,
 651                                   remote->tree->object.sha1, local_tree);
 652
 653         if (result != 0) { /* non-trivial merge (with or without conflicts) */
 654                 /* Commit (partial) result */
 655                 struct commit_list *parents = NULL;
 656                 commit_list_insert(remote, &parents); /* LIFO order */
 657                 commit_list_insert(local, &parents);
 658                 create_notes_commit(local_tree, parents, o->commit_msg.buf,
 659                                     result_sha1);
 660         }
 661
 662 found_result:
 663         free_commit_list(bases);
 664         strbuf_release(&(o->commit_msg));
 665         trace_printf("notes_merge(): result = %i, result_sha1 = %.7s\n",
 666                result, sha1_to_hex(result_sha1));
 667         return result;
 668 }
 669
 670 int notes_merge_commit(struct notes_merge_options *o,
 671                        struct notes_tree *partial_tree,
 672                        struct commit *partial_commit,
 673                        unsigned char *result_sha1)
 674 {
 675         /*
 676          * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
 677          * found notes to 'partial_tree'. Write the updates notes tree to
 678          * the DB, and commit the resulting tree object while reusing the
 679          * commit message and parents from 'partial_commit'.
 680          * Finally store the new commit object SHA1 into 'result_sha1'.
 681          */
 682         struct dir_struct dir;
 683         const char *path = git_path(NOTES_MERGE_WORKTREE "/");
 684         int path_len = strlen(path), i;
 685         const char *msg = strstr(partial_commit->buffer, "\n\n");
 686
 687         OUTPUT(o, 3, "Committing notes in notes merge worktree at %.*s",
 688                path_len - 1, path);
 689
 690         if (!msg || msg[2] == '\0')
 691                 die("partial notes commit has empty message");
 692         msg += 2;
 693
 694         memset(&dir, 0, sizeof(dir));
 695         read_directory(&dir, path, path_len, NULL);
 696         for (i = 0; i < dir.nr; i++) {
 697                 struct dir_entry *ent = dir.entries[i];
 698                 struct stat st;
 699                 const char *relpath = ent->name + path_len;
 700                 unsigned char obj_sha1[20], blob_sha1[20];
 701
 702                 if (ent->len - path_len != 40 || get_sha1_hex(relpath, obj_sha1)) {
 703                         OUTPUT(o, 3, "Skipping non-SHA1 entry '%s'", ent->name);
 704                         continue;
 705                 }
 706
 707                 /* write file as blob, and add to partial_tree */
 708                 if (stat(ent->name, &st))
 709                         die_errno("Failed to stat '%s'", ent->name);
 710                 if (index_path(blob_sha1, ent->name, &st, HASH_WRITE_OBJECT))
 711                         die("Failed to write blob object from '%s'", ent->name);
 712                 if (add_note(partial_tree, obj_sha1, blob_sha1, NULL))
 713                         die("Failed to add resolved note '%s' to notes tree",
 714                             ent->name);
 715                 OUTPUT(o, 4, "Added resolved note for object %s: %s",
 716                        sha1_to_hex(obj_sha1), sha1_to_hex(blob_sha1));
 717         }
 718
 719         create_notes_commit(partial_tree, partial_commit->parents, msg,
 720                             result_sha1);
 721         OUTPUT(o, 4, "Finalized notes merge commit: %s",
 722                sha1_to_hex(result_sha1));
 723         return 0;
 724 }
 725
 726 int notes_merge_abort(struct notes_merge_options *o)
 727 {
 728         /* Remove .git/NOTES_MERGE_WORKTREE directory and all files within */
 729         struct strbuf buf = STRBUF_INIT;
 730         int ret;
 731
 732         strbuf_addstr(&buf, git_path(NOTES_MERGE_WORKTREE));
 733         OUTPUT(o, 3, "Removing notes merge worktree at %s", buf.buf);
 734         ret = remove_dir_recursively(&buf, 0);
 735         strbuf_release(&buf);
 736         return ret;
 737 }