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 static int path_to_sha1(const char *path, unsigned char *sha1)
  25 {
  26         char hex_sha1[40];
  27         int i = 0;
  28         while (*path && i < 40) {
  29                 if (*path != '/')
  30                         hex_sha1[i++] = *path;
  31                 path++;
  32         }
  33         if (*path || i != 40)
  34                 return -1;
  35         return get_sha1_hex(hex_sha1, sha1);
  36 }
  37
  38 static int verify_notes_filepair(struct diff_filepair *p, unsigned char *sha1)
  39 {
  40         switch (p->status) {
  41         case DIFF_STATUS_MODIFIED:
  42                 assert(p->one->mode == p->two->mode);
  43                 assert(!is_null_sha1(p->one->sha1));
  44                 assert(!is_null_sha1(p->two->sha1));
  45                 break;
  46         case DIFF_STATUS_ADDED:
  47                 assert(is_null_sha1(p->one->sha1));
  48                 break;
  49         case DIFF_STATUS_DELETED:
  50                 assert(is_null_sha1(p->two->sha1));
  51                 break;
  52         default:
  53                 return -1;
  54         }
  55         assert(!strcmp(p->one->path, p->two->path));
  56         return path_to_sha1(p->one->path, sha1);
  57 }
  58
  59 static struct notes_merge_pair *find_notes_merge_pair_pos(
  60                 struct notes_merge_pair *list, int len, unsigned char *obj,
  61                 int insert_new, int *occupied)
  62 {
  63         /*
  64          * Both diff_tree_remote() and diff_tree_local() tend to process
  65          * merge_pairs in ascending order. Therefore, cache last returned
  66          * index, and search sequentially from there until the appropriate
  67          * position is found.
  68          *
  69          * Since inserts only happen from diff_tree_remote() (which mainly
  70          * _appends_), we don't care that inserting into the middle of the
  71          * list is expensive (using memmove()).
  72          */
  73         static int last_index;
  74         int i = last_index < len ? last_index : len - 1;
  75         int prev_cmp = 0, cmp = -1;
  76         while (i >= 0 && i < len) {
  77                 cmp = hashcmp(obj, list[i].obj);
  78                 if (!cmp) /* obj belongs @ i */
  79                         break;
  80                 else if (cmp < 0 && prev_cmp <= 0) /* obj belongs < i */
  81                         i--;
  82                 else if (cmp < 0) /* obj belongs between i-1 and i */
  83                         break;
  84                 else if (cmp > 0 && prev_cmp >= 0) /* obj belongs > i */
  85                         i++;
  86                 else /* if (cmp > 0) */ { /* obj belongs between i and i+1 */
  87                         i++;
  88                         break;
  89                 }
  90                 prev_cmp = cmp;
  91         }
  92         if (i < 0)
  93                 i = 0;
  94         /* obj belongs at, or immediately preceding, index i (0 <= i <= len) */
  95
  96         if (!cmp)
  97                 *occupied = 1;
  98         else {
  99                 *occupied = 0;
 100                 if (insert_new && i < len) {
 101                         memmove(list + i + 1, list + i,
 102                                 (len - i) * sizeof(struct notes_merge_pair));
 103                         memset(list + i, 0, sizeof(struct notes_merge_pair));
 104                 }
 105         }
 106         last_index = i;
 107         return list + i;
 108 }
 109
 110 static unsigned char uninitialized[20] =
 111         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
 112         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff";
 113
 114 static struct notes_merge_pair *diff_tree_remote(struct notes_merge_options *o,
 115                                                  const unsigned char *base,
 116                                                  const unsigned char *remote,
 117                                                  int *num_changes)
 118 {
 119         struct diff_options opt;
 120         struct notes_merge_pair *changes;
 121         int i, len = 0;
 122
 123         trace_printf("\tdiff_tree_remote(base = %.7s, remote = %.7s)\n",
 124                sha1_to_hex(base), sha1_to_hex(remote));
 125
 126         diff_setup(&opt);
 127         DIFF_OPT_SET(&opt, RECURSIVE);
 128         opt.output_format = DIFF_FORMAT_NO_OUTPUT;
 129         if (diff_setup_done(&opt) < 0)
 130                 die("diff_setup_done failed");
 131         diff_tree_sha1(base, remote, "", &opt);
 132         diffcore_std(&opt);
 133
 134         changes = xcalloc(diff_queued_diff.nr, sizeof(struct notes_merge_pair));
 135
 136         for (i = 0; i < diff_queued_diff.nr; i++) {
 137                 struct diff_filepair *p = diff_queued_diff.queue[i];
 138                 struct notes_merge_pair *mp;
 139                 int occupied;
 140                 unsigned char obj[20];
 141
 142                 if (verify_notes_filepair(p, obj)) {
 143                         trace_printf("\t\tCannot merge entry '%s' (%c): "
 144                                "%.7s -> %.7s. Skipping!\n", p->one->path,
 145                                p->status, sha1_to_hex(p->one->sha1),
 146                                sha1_to_hex(p->two->sha1));
 147                         continue;
 148                 }
 149                 mp = find_notes_merge_pair_pos(changes, len, obj, 1, &occupied);
 150                 if (occupied) {
 151                         /* We've found an addition/deletion pair */
 152                         assert(!hashcmp(mp->obj, obj));
 153                         if (is_null_sha1(p->one->sha1)) { /* addition */
 154                                 assert(is_null_sha1(mp->remote));
 155                                 hashcpy(mp->remote, p->two->sha1);
 156                         } else if (is_null_sha1(p->two->sha1)) { /* deletion */
 157                                 assert(is_null_sha1(mp->base));
 158                                 hashcpy(mp->base, p->one->sha1);
 159                         } else
 160                                 assert(!"Invalid existing change recorded");
 161                 } else {
 162                         hashcpy(mp->obj, obj);
 163                         hashcpy(mp->base, p->one->sha1);
 164                         hashcpy(mp->local, uninitialized);
 165                         hashcpy(mp->remote, p->two->sha1);
 166                         len++;
 167                 }
 168                 trace_printf("\t\tStored remote change for %s: %.7s -> %.7s\n",
 169                        sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
 170                        sha1_to_hex(mp->remote));
 171         }
 172         diff_flush(&opt);
 173         diff_tree_release_paths(&opt);
 174
 175         *num_changes = len;
 176         return changes;
 177 }
 178
 179 static void diff_tree_local(struct notes_merge_options *o,
 180                             struct notes_merge_pair *changes, int len,
 181                             const unsigned char *base,
 182                             const unsigned char *local)
 183 {
 184         struct diff_options opt;
 185         int i;
 186
 187         trace_printf("\tdiff_tree_local(len = %i, base = %.7s, local = %.7s)\n",
 188                len, sha1_to_hex(base), sha1_to_hex(local));
 189
 190         diff_setup(&opt);
 191         DIFF_OPT_SET(&opt, RECURSIVE);
 192         opt.output_format = DIFF_FORMAT_NO_OUTPUT;
 193         if (diff_setup_done(&opt) < 0)
 194                 die("diff_setup_done failed");
 195         diff_tree_sha1(base, local, "", &opt);
 196         diffcore_std(&opt);
 197
 198         for (i = 0; i < diff_queued_diff.nr; i++) {
 199                 struct diff_filepair *p = diff_queued_diff.queue[i];
 200                 struct notes_merge_pair *mp;
 201                 int match;
 202                 unsigned char obj[20];
 203
 204                 if (verify_notes_filepair(p, obj)) {
 205                         trace_printf("\t\tCannot merge entry '%s' (%c): "
 206                                "%.7s -> %.7s. Skipping!\n", p->one->path,
 207                                p->status, sha1_to_hex(p->one->sha1),
 208                                sha1_to_hex(p->two->sha1));
 209                         continue;
 210                 }
 211                 mp = find_notes_merge_pair_pos(changes, len, obj, 0, &match);
 212                 if (!match) {
 213                         trace_printf("\t\tIgnoring local-only change for %s: "
 214                                "%.7s -> %.7s\n", sha1_to_hex(obj),
 215                                sha1_to_hex(p->one->sha1),
 216                                sha1_to_hex(p->two->sha1));
 217                         continue;
 218                 }
 219
 220                 assert(!hashcmp(mp->obj, obj));
 221                 if (is_null_sha1(p->two->sha1)) { /* deletion */
 222                         /*
 223                          * Either this is a true deletion (1), or it is part
 224                          * of an A/D pair (2), or D/A pair (3):
 225                          *
 226                          * (1) mp->local is uninitialized; set it to null_sha1
 227                          * (2) mp->local is not uninitialized; don't touch it
 228                          * (3) mp->local is uninitialized; set it to null_sha1
 229                          *     (will be overwritten by following addition)
 230                          */
 231                         if (!hashcmp(mp->local, uninitialized))
 232                                 hashclr(mp->local);
 233                 } else if (is_null_sha1(p->one->sha1)) { /* addition */
 234                         /*
 235                          * Either this is a true addition (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 to p->two->sha1
 239                          * (2) mp->local is uninitialized; set to p->two->sha1
 240                          * (3) mp->local is null_sha1;     set to p->two->sha1
 241                          */
 242                         assert(is_null_sha1(mp->local) ||
 243                                !hashcmp(mp->local, uninitialized));
 244                         hashcpy(mp->local, p->two->sha1);
 245                 } else { /* modification */
 246                         /*
 247                          * This is a true modification. p->one->sha1 shall
 248                          * match mp->base, and mp->local shall be uninitialized.
 249                          * Set mp->local to p->two->sha1.
 250                          */
 251                         assert(!hashcmp(p->one->sha1, mp->base));
 252                         assert(!hashcmp(mp->local, uninitialized));
 253                         hashcpy(mp->local, p->two->sha1);
 254                 }
 255                 trace_printf("\t\tStored local change for %s: %.7s -> %.7s\n",
 256                        sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
 257                        sha1_to_hex(mp->local));
 258         }
 259         diff_flush(&opt);
 260         diff_tree_release_paths(&opt);
 261 }
 262
 263 static void check_notes_merge_worktree(struct notes_merge_options *o)
 264 {
 265         if (!o->has_worktree) {
 266                 /*
 267                  * Must establish NOTES_MERGE_WORKTREE.
 268                  * Abort if NOTES_MERGE_WORKTREE already exists
 269                  */
 270                 if (file_exists(git_path(NOTES_MERGE_WORKTREE))) {
 271                         if (advice_resolve_conflict)
 272                                 die("You have not concluded your previous "
 273                                     "notes merge (%s exists).\nPlease, use "
 274                                     "'git notes merge --commit' or 'git notes "
 275                                     "merge --abort' to commit/abort the "
 276                                     "previous merge before you start a new "
 277                                     "notes merge.", git_path("NOTES_MERGE_*"));
 278                         else
 279                                 die("You have not concluded your notes merge "
 280                                     "(%s exists).", git_path("NOTES_MERGE_*"));
 281                 }
 282
 283                 if (safe_create_leading_directories(git_path(
 284                                 NOTES_MERGE_WORKTREE "/.test")))
 285                         die_errno("unable to create directory %s",
 286                                   git_path(NOTES_MERGE_WORKTREE));
 287                 o->has_worktree = 1;
 288         } else if (!file_exists(git_path(NOTES_MERGE_WORKTREE)))
 289                 /* NOTES_MERGE_WORKTREE should already be established */
 290                 die("missing '%s'. This should not happen",
 291                     git_path(NOTES_MERGE_WORKTREE));
 292 }
 293
 294 static void write_buf_to_worktree(const unsigned char *obj,
 295                                   const char *buf, unsigned long size)
 296 {
 297         int fd;
 298         char *path = git_path(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
 299         if (safe_create_leading_directories(path))
 300                 die_errno("unable to create directory for '%s'", path);
 301         if (file_exists(path))
 302                 die("found existing file at '%s'", path);
 303
 304         fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, 0666);
 305         if (fd < 0)
 306                 die_errno("failed to open '%s'", path);
 307
 308         while (size > 0) {
 309                 long ret = write_in_full(fd, buf, size);
 310                 if (ret < 0) {
 311                         /* Ignore epipe */
 312                         if (errno == EPIPE)
 313                                 break;
 314                         die_errno("notes-merge");
 315                 } else if (!ret) {
 316                         die("notes-merge: disk full?");
 317                 }
 318                 size -= ret;
 319                 buf += ret;
 320         }
 321
 322         close(fd);
 323 }
 324
 325 static void write_note_to_worktree(const unsigned char *obj,
 326                                    const unsigned char *note)
 327 {
 328         enum object_type type;
 329         unsigned long size;
 330         void *buf = read_sha1_file(note, &type, &size);
 331
 332         if (!buf)
 333                 die("cannot read note %s for object %s",
 334                     sha1_to_hex(note), sha1_to_hex(obj));
 335         if (type != OBJ_BLOB)
 336                 die("blob expected in note %s for object %s",
 337                     sha1_to_hex(note), sha1_to_hex(obj));
 338         write_buf_to_worktree(obj, buf, size);
 339         free(buf);
 340 }
 341
 342 static int ll_merge_in_worktree(struct notes_merge_options *o,
 343                                 struct notes_merge_pair *p)
 344 {
 345         mmbuffer_t result_buf;
 346         mmfile_t base, local, remote;
 347         int status;
 348
 349         read_mmblob(&base, p->base);
 350         read_mmblob(&local, p->local);
 351         read_mmblob(&remote, p->remote);
 352
 353         status = ll_merge(&result_buf, sha1_to_hex(p->obj), &base, NULL,
 354                           &local, o->local_ref, &remote, o->remote_ref, NULL);
 355
 356         free(base.ptr);
 357         free(local.ptr);
 358         free(remote.ptr);
 359
 360         if ((status < 0) || !result_buf.ptr)
 361                 die("Failed to execute internal merge");
 362
 363         write_buf_to_worktree(p->obj, result_buf.ptr, result_buf.size);
 364         free(result_buf.ptr);
 365
 366         return status;
 367 }
 368
 369 static int merge_one_change_manual(struct notes_merge_options *o,
 370                                    struct notes_merge_pair *p,
 371                                    struct notes_tree *t)
 372 {
 373         const char *lref = o->local_ref ? o->local_ref : "local version";
 374         const char *rref = o->remote_ref ? o->remote_ref : "remote version";
 375
 376         trace_printf("\t\t\tmerge_one_change_manual(obj = %.7s, base = %.7s, "
 377                "local = %.7s, remote = %.7s)\n",
 378                sha1_to_hex(p->obj), sha1_to_hex(p->base),
 379                sha1_to_hex(p->local), sha1_to_hex(p->remote));
 380
 381         /* add "Conflicts:" section to commit message first time through */
 382         if (!o->has_worktree)
 383                 strbuf_addstr(&(o->commit_msg), "\n\nConflicts:\n");
 384
 385         strbuf_addf(&(o->commit_msg), "\t%s\n", sha1_to_hex(p->obj));
 386
 387         if (o->verbosity >= 2)
 388                 printf("Auto-merging notes for %s\n", sha1_to_hex(p->obj));
 389         check_notes_merge_worktree(o);
 390         if (is_null_sha1(p->local)) {
 391                 /* D/F conflict, checkout p->remote */
 392                 assert(!is_null_sha1(p->remote));
 393                 if (o->verbosity >= 1)
 394                         printf("CONFLICT (delete/modify): Notes for object %s "
 395                                 "deleted in %s and modified in %s. Version from %s "
 396                                 "left in tree.\n",
 397                                 sha1_to_hex(p->obj), lref, rref, rref);
 398                 write_note_to_worktree(p->obj, p->remote);
 399         } else if (is_null_sha1(p->remote)) {
 400                 /* D/F conflict, checkout p->local */
 401                 assert(!is_null_sha1(p->local));
 402                 if (o->verbosity >= 1)
 403                         printf("CONFLICT (delete/modify): Notes for object %s "
 404                                 "deleted in %s and modified in %s. Version from %s "
 405                                 "left in tree.\n",
 406                                 sha1_to_hex(p->obj), rref, lref, lref);
 407                 write_note_to_worktree(p->obj, p->local);
 408         } else {
 409                 /* "regular" conflict, checkout result of ll_merge() */
 410                 const char *reason = "content";
 411                 if (is_null_sha1(p->base))
 412                         reason = "add/add";
 413                 assert(!is_null_sha1(p->local));
 414                 assert(!is_null_sha1(p->remote));
 415                 if (o->verbosity >= 1)
 416                         printf("CONFLICT (%s): Merge conflict in notes for "
 417                                 "object %s\n", reason, sha1_to_hex(p->obj));
 418                 ll_merge_in_worktree(o, p);
 419         }
 420
 421         trace_printf("\t\t\tremoving from partial merge result\n");
 422         remove_note(t, p->obj);
 423
 424         return 1;
 425 }
 426
 427 static int merge_one_change(struct notes_merge_options *o,
 428                             struct notes_merge_pair *p, struct notes_tree *t)
 429 {
 430         /*
 431          * Return 0 if change is successfully resolved (stored in notes_tree).
 432          * Return 1 is change results in a conflict (NOT stored in notes_tree,
 433          * but instead written to NOTES_MERGE_WORKTREE with conflict markers).
 434          */
 435         switch (o->strategy) {
 436         case NOTES_MERGE_RESOLVE_MANUAL:
 437                 return merge_one_change_manual(o, p, t);
 438         case NOTES_MERGE_RESOLVE_OURS:
 439                 if (o->verbosity >= 2)
 440                         printf("Using local notes for %s\n",
 441                                                 sha1_to_hex(p->obj));
 442                 /* nothing to do */
 443                 return 0;
 444         case NOTES_MERGE_RESOLVE_THEIRS:
 445                 if (o->verbosity >= 2)
 446                         printf("Using remote notes for %s\n",
 447                                                 sha1_to_hex(p->obj));
 448                 if (add_note(t, p->obj, p->remote, combine_notes_overwrite))
 449                         die("BUG: combine_notes_overwrite failed");
 450                 return 0;
 451         case NOTES_MERGE_RESOLVE_UNION:
 452                 if (o->verbosity >= 2)
 453                         printf("Concatenating local and remote notes for %s\n",
 454                                                         sha1_to_hex(p->obj));
 455                 if (add_note(t, p->obj, p->remote, combine_notes_concatenate))
 456                         die("failed to concatenate notes "
 457                             "(combine_notes_concatenate)");
 458                 return 0;
 459         case NOTES_MERGE_RESOLVE_CAT_SORT_UNIQ:
 460                 if (o->verbosity >= 2)
 461                         printf("Concatenating unique lines in local and remote "
 462                                 "notes for %s\n", sha1_to_hex(p->obj));
 463                 if (add_note(t, p->obj, p->remote, combine_notes_cat_sort_uniq))
 464                         die("failed to concatenate notes "
 465                             "(combine_notes_cat_sort_uniq)");
 466                 return 0;
 467         }
 468         die("Unknown strategy (%i).", o->strategy);
 469 }
 470
 471 static int merge_changes(struct notes_merge_options *o,
 472                          struct notes_merge_pair *changes, int *num_changes,
 473                          struct notes_tree *t)
 474 {
 475         int i, conflicts = 0;
 476
 477         trace_printf("\tmerge_changes(num_changes = %i)\n", *num_changes);
 478         for (i = 0; i < *num_changes; i++) {
 479                 struct notes_merge_pair *p = changes + i;
 480                 trace_printf("\t\t%.7s: %.7s -> %.7s/%.7s\n",
 481                        sha1_to_hex(p->obj), sha1_to_hex(p->base),
 482                        sha1_to_hex(p->local), sha1_to_hex(p->remote));
 483
 484                 if (!hashcmp(p->base, p->remote)) {
 485                         /* no remote change; nothing to do */
 486                         trace_printf("\t\t\tskipping (no remote change)\n");
 487                 } else if (!hashcmp(p->local, p->remote)) {
 488                         /* same change in local and remote; nothing to do */
 489                         trace_printf("\t\t\tskipping (local == remote)\n");
 490                 } else if (!hashcmp(p->local, uninitialized) ||
 491                            !hashcmp(p->local, p->base)) {
 492                         /* no local change; adopt remote change */
 493                         trace_printf("\t\t\tno local change, adopted remote\n");
 494                         if (add_note(t, p->obj, p->remote,
 495                                      combine_notes_overwrite))
 496                                 die("BUG: combine_notes_overwrite failed");
 497                 } else {
 498                         /* need file-level merge between local and remote */
 499                         trace_printf("\t\t\tneed content-level merge\n");
 500                         conflicts += merge_one_change(o, p, t);
 501                 }
 502         }
 503
 504         return conflicts;
 505 }
 506
 507 static int merge_from_diffs(struct notes_merge_options *o,
 508                             const unsigned char *base,
 509                             const unsigned char *local,
 510                             const unsigned char *remote, struct notes_tree *t)
 511 {
 512         struct notes_merge_pair *changes;
 513         int num_changes, conflicts;
 514
 515         trace_printf("\tmerge_from_diffs(base = %.7s, local = %.7s, "
 516                "remote = %.7s)\n", sha1_to_hex(base), sha1_to_hex(local),
 517                sha1_to_hex(remote));
 518
 519         changes = diff_tree_remote(o, base, remote, &num_changes);
 520         diff_tree_local(o, changes, num_changes, base, local);
 521
 522         conflicts = merge_changes(o, changes, &num_changes, t);
 523         free(changes);
 524
 525         if (o->verbosity >= 4)
 526                 printf("Merge result: %i unmerged notes and a %s notes tree\n",
 527                         conflicts, t->dirty ? "dirty" : "clean");
 528
 529         return conflicts ? -1 : 1;
 530 }
 531
 532 void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 533                          const char *msg, unsigned char *result_sha1)
 534 {
 535         unsigned char tree_sha1[20];
 536
 537         assert(t->initialized);
 538
 539         if (write_notes_tree(t, tree_sha1))
 540                 die("Failed to write notes tree to database");
 541
 542         if (!parents) {
 543                 /* Deduce parent commit from t->ref */
 544                 unsigned char parent_sha1[20];
 545                 if (!read_ref(t->ref, parent_sha1)) {
 546                         struct commit *parent = lookup_commit(parent_sha1);
 547                         if (!parent || parse_commit(parent))
 548                                 die("Failed to find/parse commit %s", t->ref);
 549                         commit_list_insert(parent, &parents);
 550                 }
 551                 /* else: t->ref points to nothing, assume root/orphan commit */
 552         }
 553
 554         if (commit_tree(msg, tree_sha1, parents, result_sha1, NULL))
 555                 die("Failed to commit notes tree to database");
 556 }
 557
 558 int notes_merge(struct notes_merge_options *o,
 559                 struct notes_tree *local_tree,
 560                 unsigned char *result_sha1)
 561 {
 562         unsigned char local_sha1[20], remote_sha1[20];
 563         struct commit *local, *remote;
 564         struct commit_list *bases = NULL;
 565         const unsigned char *base_sha1, *base_tree_sha1;
 566         int result = 0;
 567
 568         assert(o->local_ref && o->remote_ref);
 569         assert(!strcmp(o->local_ref, local_tree->ref));
 570         hashclr(result_sha1);
 571
 572         trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
 573                o->local_ref, o->remote_ref);
 574
 575         /* Dereference o->local_ref into local_sha1 */
 576         if (!resolve_ref(o->local_ref, local_sha1, 0, NULL))
 577                 die("Failed to resolve local notes ref '%s'", o->local_ref);
 578         else if (!check_ref_format(o->local_ref) && is_null_sha1(local_sha1))
 579                 local = NULL; /* local_sha1 == null_sha1 indicates unborn ref */
 580         else if (!(local = lookup_commit_reference(local_sha1)))
 581                 die("Could not parse local commit %s (%s)",
 582                     sha1_to_hex(local_sha1), o->local_ref);
 583         trace_printf("\tlocal commit: %.7s\n", sha1_to_hex(local_sha1));
 584
 585         /* Dereference o->remote_ref into remote_sha1 */
 586         if (get_sha1(o->remote_ref, remote_sha1)) {
 587                 /*
 588                  * Failed to get remote_sha1. If o->remote_ref looks like an
 589                  * unborn ref, perform the merge using an empty notes tree.
 590                  */
 591                 if (!check_ref_format(o->remote_ref)) {
 592                         hashclr(remote_sha1);
 593                         remote = NULL;
 594                 } else {
 595                         die("Failed to resolve remote notes ref '%s'",
 596                             o->remote_ref);
 597                 }
 598         } else if (!(remote = lookup_commit_reference(remote_sha1))) {
 599                 die("Could not parse remote commit %s (%s)",
 600                     sha1_to_hex(remote_sha1), o->remote_ref);
 601         }
 602         trace_printf("\tremote commit: %.7s\n", sha1_to_hex(remote_sha1));
 603
 604         if (!local && !remote)
 605                 die("Cannot merge empty notes ref (%s) into empty notes ref "
 606                     "(%s)", o->remote_ref, o->local_ref);
 607         if (!local) {
 608                 /* result == remote commit */
 609                 hashcpy(result_sha1, remote_sha1);
 610                 goto found_result;
 611         }
 612         if (!remote) {
 613                 /* result == local commit */
 614                 hashcpy(result_sha1, local_sha1);
 615                 goto found_result;
 616         }
 617         assert(local && remote);
 618
 619         /* Find merge bases */
 620         bases = get_merge_bases(local, remote, 1);
 621         if (!bases) {
 622                 base_sha1 = null_sha1;
 623                 base_tree_sha1 = EMPTY_TREE_SHA1_BIN;
 624                 if (o->verbosity >= 4)
 625                         printf("No merge base found; doing history-less merge\n");
 626         } else if (!bases->next) {
 627                 base_sha1 = bases->item->object.sha1;
 628                 base_tree_sha1 = bases->item->tree->object.sha1;
 629                 if (o->verbosity >= 4)
 630                         printf("One merge base found (%.7s)\n",
 631                                 sha1_to_hex(base_sha1));
 632         } else {
 633                 /* TODO: How to handle multiple merge-bases? */
 634                 base_sha1 = bases->item->object.sha1;
 635                 base_tree_sha1 = bases->item->tree->object.sha1;
 636                 if (o->verbosity >= 3)
 637                         printf("Multiple merge bases found. Using the first "
 638                                 "(%.7s)\n", sha1_to_hex(base_sha1));
 639         }
 640
 641         if (o->verbosity >= 4)
 642                 printf("Merging remote commit %.7s into local commit %.7s with "
 643                         "merge-base %.7s\n", sha1_to_hex(remote->object.sha1),
 644                         sha1_to_hex(local->object.sha1),
 645                         sha1_to_hex(base_sha1));
 646
 647         if (!hashcmp(remote->object.sha1, base_sha1)) {
 648                 /* Already merged; result == local commit */
 649                 if (o->verbosity >= 2)
 650                         printf("Already up-to-date!\n");
 651                 hashcpy(result_sha1, local->object.sha1);
 652                 goto found_result;
 653         }
 654         if (!hashcmp(local->object.sha1, base_sha1)) {
 655                 /* Fast-forward; result == remote commit */
 656                 if (o->verbosity >= 2)
 657                         printf("Fast-forward\n");
 658                 hashcpy(result_sha1, remote->object.sha1);
 659                 goto found_result;
 660         }
 661
 662         result = merge_from_diffs(o, base_tree_sha1, local->tree->object.sha1,
 663                                   remote->tree->object.sha1, local_tree);
 664
 665         if (result != 0) { /* non-trivial merge (with or without conflicts) */
 666                 /* Commit (partial) result */
 667                 struct commit_list *parents = NULL;
 668                 commit_list_insert(remote, &parents); /* LIFO order */
 669                 commit_list_insert(local, &parents);
 670                 create_notes_commit(local_tree, parents, o->commit_msg.buf,
 671                                     result_sha1);
 672         }
 673
 674 found_result:
 675         free_commit_list(bases);
 676         strbuf_release(&(o->commit_msg));
 677         trace_printf("notes_merge(): result = %i, result_sha1 = %.7s\n",
 678                result, sha1_to_hex(result_sha1));
 679         return result;
 680 }
 681
 682 int notes_merge_commit(struct notes_merge_options *o,
 683                        struct notes_tree *partial_tree,
 684                        struct commit *partial_commit,
 685                        unsigned char *result_sha1)
 686 {
 687         /*
 688          * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
 689          * found notes to 'partial_tree'. Write the updates notes tree to
 690          * the DB, and commit the resulting tree object while reusing the
 691          * commit message and parents from 'partial_commit'.
 692          * Finally store the new commit object SHA1 into 'result_sha1'.
 693          */
 694         struct dir_struct dir;
 695         char *path = xstrdup(git_path(NOTES_MERGE_WORKTREE "/"));
 696         int path_len = strlen(path), i;
 697         const char *msg = strstr(partial_commit->buffer, "\n\n");
 698
 699         if (o->verbosity >= 3)
 700                 printf("Committing notes in notes merge worktree at %.*s\n",
 701                         path_len - 1, path);
 702
 703         if (!msg || msg[2] == '\0')
 704                 die("partial notes commit has empty message");
 705         msg += 2;
 706
 707         memset(&dir, 0, sizeof(dir));
 708         read_directory(&dir, path, path_len, NULL);
 709         for (i = 0; i < dir.nr; i++) {
 710                 struct dir_entry *ent = dir.entries[i];
 711                 struct stat st;
 712                 const char *relpath = ent->name + path_len;
 713                 unsigned char obj_sha1[20], blob_sha1[20];
 714
 715                 if (ent->len - path_len != 40 || get_sha1_hex(relpath, obj_sha1)) {
 716                         if (o->verbosity >= 3)
 717                                 printf("Skipping non-SHA1 entry '%s'\n",
 718                                                                 ent->name);
 719                         continue;
 720                 }
 721
 722                 /* write file as blob, and add to partial_tree */
 723                 if (stat(ent->name, &st))
 724                         die_errno("Failed to stat '%s'", ent->name);
 725                 if (index_path(blob_sha1, ent->name, &st, HASH_WRITE_OBJECT))
 726                         die("Failed to write blob object from '%s'", ent->name);
 727                 if (add_note(partial_tree, obj_sha1, blob_sha1, NULL))
 728                         die("Failed to add resolved note '%s' to notes tree",
 729                             ent->name);
 730                 if (o->verbosity >= 4)
 731                         printf("Added resolved note for object %s: %s\n",
 732                                 sha1_to_hex(obj_sha1), sha1_to_hex(blob_sha1));
 733         }
 734
 735         create_notes_commit(partial_tree, partial_commit->parents, msg,
 736                             result_sha1);
 737         if (o->verbosity >= 4)
 738                 printf("Finalized notes merge commit: %s\n",
 739                         sha1_to_hex(result_sha1));
 740         free(path);
 741         return 0;
 742 }
 743
 744 int notes_merge_abort(struct notes_merge_options *o)
 745 {
 746         /* Remove .git/NOTES_MERGE_WORKTREE directory and all files within */
 747         struct strbuf buf = STRBUF_INIT;
 748         int ret;
 749
 750         strbuf_addstr(&buf, git_path(NOTES_MERGE_WORKTREE));
 751         if (o->verbosity >= 3)
 752                 printf("Removing notes merge worktree at %s\n", buf.buf);
 753         ret = remove_dir_recursively(&buf, 0);
 754         strbuf_release(&buf);
 755         return ret;
 756 }