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 #include "notes-utils.h"
  13
  14 struct notes_merge_pair {
  15         unsigned char obj[20], base[20], local[20], remote[20];
  16 };
  17
  18 void init_notes_merge_options(struct notes_merge_options *o)
  19 {
  20         memset(o, 0, sizeof(struct notes_merge_options));
  21         strbuf_init(&(o->commit_msg), 0);
  22         o->verbosity = NOTES_MERGE_VERBOSITY_DEFAULT;
  23 }
  24
  25 static int path_to_sha1(const char *path, unsigned char *sha1)
  26 {
  27         char hex_sha1[40];
  28         int i = 0;
  29         while (*path && i < 40) {
  30                 if (*path != '/')
  31                         hex_sha1[i++] = *path;
  32                 path++;
  33         }
  34         if (*path || i != 40)
  35                 return -1;
  36         return get_sha1_hex(hex_sha1, sha1);
  37 }
  38
  39 static int verify_notes_filepair(struct diff_filepair *p, unsigned char *sha1)
  40 {
  41         switch (p->status) {
  42         case DIFF_STATUS_MODIFIED:
  43                 assert(p->one->mode == p->two->mode);
  44                 assert(!is_null_oid(&p->one->oid));
  45                 assert(!is_null_oid(&p->two->oid));
  46                 break;
  47         case DIFF_STATUS_ADDED:
  48                 assert(is_null_oid(&p->one->oid));
  49                 break;
  50         case DIFF_STATUS_DELETED:
  51                 assert(is_null_oid(&p->two->oid));
  52                 break;
  53         default:
  54                 return -1;
  55         }
  56         assert(!strcmp(p->one->path, p->two->path));
  57         return path_to_sha1(p->one->path, sha1);
  58 }
  59
  60 static struct notes_merge_pair *find_notes_merge_pair_pos(
  61                 struct notes_merge_pair *list, int len, unsigned char *obj,
  62                 int insert_new, int *occupied)
  63 {
  64         /*
  65          * Both diff_tree_remote() and diff_tree_local() tend to process
  66          * merge_pairs in ascending order. Therefore, cache last returned
  67          * index, and search sequentially from there until the appropriate
  68          * position is found.
  69          *
  70          * Since inserts only happen from diff_tree_remote() (which mainly
  71          * _appends_), we don't care that inserting into the middle of the
  72          * list is expensive (using memmove()).
  73          */
  74         static int last_index;
  75         int i = last_index < len ? last_index : len - 1;
  76         int prev_cmp = 0, cmp = -1;
  77         while (i >= 0 && i < len) {
  78                 cmp = hashcmp(obj, list[i].obj);
  79                 if (!cmp) /* obj belongs @ i */
  80                         break;
  81                 else if (cmp < 0 && prev_cmp <= 0) /* obj belongs < i */
  82                         i--;
  83                 else if (cmp < 0) /* obj belongs between i-1 and i */
  84                         break;
  85                 else if (cmp > 0 && prev_cmp >= 0) /* obj belongs > i */
  86                         i++;
  87                 else /* if (cmp > 0) */ { /* obj belongs between i and i+1 */
  88                         i++;
  89                         break;
  90                 }
  91                 prev_cmp = cmp;
  92         }
  93         if (i < 0)
  94                 i = 0;
  95         /* obj belongs at, or immediately preceding, index i (0 <= i <= len) */
  96
  97         if (!cmp)
  98                 *occupied = 1;
  99         else {
 100                 *occupied = 0;
 101                 if (insert_new && i < len) {
 102                         memmove(list + i + 1, list + i,
 103                                 (len - i) * sizeof(struct notes_merge_pair));
 104                         memset(list + i, 0, sizeof(struct notes_merge_pair));
 105                 }
 106         }
 107         last_index = i;
 108         return list + i;
 109 }
 110
 111 static unsigned char uninitialized[20] =
 112         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" \
 113         "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff";
 114
 115 static struct notes_merge_pair *diff_tree_remote(struct notes_merge_options *o,
 116                                                  const unsigned char *base,
 117                                                  const unsigned char *remote,
 118                                                  int *num_changes)
 119 {
 120         struct diff_options opt;
 121         struct notes_merge_pair *changes;
 122         int i, len = 0;
 123
 124         trace_printf("\tdiff_tree_remote(base = %.7s, remote = %.7s)\n",
 125                sha1_to_hex(base), sha1_to_hex(remote));
 126
 127         diff_setup(&opt);
 128         DIFF_OPT_SET(&opt, RECURSIVE);
 129         opt.output_format = DIFF_FORMAT_NO_OUTPUT;
 130         diff_setup_done(&opt);
 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, oid_to_hex(&p->one->oid),
 146                                oid_to_hex(&p->two->oid));
 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_oid(&p->one->oid)) { /* addition */
 154                                 assert(is_null_sha1(mp->remote));
 155                                 hashcpy(mp->remote, p->two->oid.hash);
 156                         } else if (is_null_oid(&p->two->oid)) { /* deletion */
 157                                 assert(is_null_sha1(mp->base));
 158                                 hashcpy(mp->base, p->one->oid.hash);
 159                         } else
 160                                 assert(!"Invalid existing change recorded");
 161                 } else {
 162                         hashcpy(mp->obj, obj);
 163                         hashcpy(mp->base, p->one->oid.hash);
 164                         hashcpy(mp->local, uninitialized);
 165                         hashcpy(mp->remote, p->two->oid.hash);
 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         clear_pathspec(&opt.pathspec);
 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         diff_setup_done(&opt);
 194         diff_tree_sha1(base, local, "", &opt);
 195         diffcore_std(&opt);
 196
 197         for (i = 0; i < diff_queued_diff.nr; i++) {
 198                 struct diff_filepair *p = diff_queued_diff.queue[i];
 199                 struct notes_merge_pair *mp;
 200                 int match;
 201                 unsigned char obj[20];
 202
 203                 if (verify_notes_filepair(p, obj)) {
 204                         trace_printf("\t\tCannot merge entry '%s' (%c): "
 205                                "%.7s -> %.7s. Skipping!\n", p->one->path,
 206                                p->status, oid_to_hex(&p->one->oid),
 207                                oid_to_hex(&p->two->oid));
 208                         continue;
 209                 }
 210                 mp = find_notes_merge_pair_pos(changes, len, obj, 0, &match);
 211                 if (!match) {
 212                         trace_printf("\t\tIgnoring local-only change for %s: "
 213                                "%.7s -> %.7s\n", sha1_to_hex(obj),
 214                                oid_to_hex(&p->one->oid),
 215                                oid_to_hex(&p->two->oid));
 216                         continue;
 217                 }
 218
 219                 assert(!hashcmp(mp->obj, obj));
 220                 if (is_null_oid(&p->two->oid)) { /* deletion */
 221                         /*
 222                          * Either this is a true deletion (1), or it is part
 223                          * of an A/D pair (2), or D/A pair (3):
 224                          *
 225                          * (1) mp->local is uninitialized; set it to null_sha1
 226                          * (2) mp->local is not uninitialized; don't touch it
 227                          * (3) mp->local is uninitialized; set it to null_sha1
 228                          *     (will be overwritten by following addition)
 229                          */
 230                         if (!hashcmp(mp->local, uninitialized))
 231                                 hashclr(mp->local);
 232                 } else if (is_null_oid(&p->one->oid)) { /* addition */
 233                         /*
 234                          * Either this is a true addition (1), or it is part
 235                          * of an A/D pair (2), or D/A pair (3):
 236                          *
 237                          * (1) mp->local is uninitialized; set to p->two->sha1
 238                          * (2) mp->local is uninitialized; set to p->two->sha1
 239                          * (3) mp->local is null_sha1;     set to p->two->sha1
 240                          */
 241                         assert(is_null_sha1(mp->local) ||
 242                                !hashcmp(mp->local, uninitialized));
 243                         hashcpy(mp->local, p->two->oid.hash);
 244                 } else { /* modification */
 245                         /*
 246                          * This is a true modification. p->one->sha1 shall
 247                          * match mp->base, and mp->local shall be uninitialized.
 248                          * Set mp->local to p->two->sha1.
 249                          */
 250                         assert(!hashcmp(p->one->oid.hash, mp->base));
 251                         assert(!hashcmp(mp->local, uninitialized));
 252                         hashcpy(mp->local, p->two->oid.hash);
 253                 }
 254                 trace_printf("\t\tStored local change for %s: %.7s -> %.7s\n",
 255                        sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
 256                        sha1_to_hex(mp->local));
 257         }
 258         diff_flush(&opt);
 259         clear_pathspec(&opt.pathspec);
 260 }
 261
 262 static void check_notes_merge_worktree(struct notes_merge_options *o)
 263 {
 264         if (!o->has_worktree) {
 265                 /*
 266                  * Must establish NOTES_MERGE_WORKTREE.
 267                  * Abort if NOTES_MERGE_WORKTREE already exists
 268                  */
 269                 if (file_exists(git_path(NOTES_MERGE_WORKTREE)) &&
 270                     !is_empty_dir(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_const(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_pathdup(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
 299         if (safe_create_leading_directories_const(path))
 300                 die_errno("unable to create directory for '%s'", path);
 301
 302         fd = xopen(path, O_WRONLY | O_EXCL | O_CREAT, 0666);
 303
 304         while (size > 0) {
 305                 long ret = write_in_full(fd, buf, size);
 306                 if (ret < 0) {
 307                         /* Ignore epipe */
 308                         if (errno == EPIPE)
 309                                 break;
 310                         die_errno("notes-merge");
 311                 } else if (!ret) {
 312                         die("notes-merge: disk full?");
 313                 }
 314                 size -= ret;
 315                 buf += ret;
 316         }
 317
 318         close(fd);
 319         free(path);
 320 }
 321
 322 static void write_note_to_worktree(const unsigned char *obj,
 323                                    const unsigned char *note)
 324 {
 325         enum object_type type;
 326         unsigned long size;
 327         void *buf = read_sha1_file(note, &type, &size);
 328
 329         if (!buf)
 330                 die("cannot read note %s for object %s",
 331                     sha1_to_hex(note), sha1_to_hex(obj));
 332         if (type != OBJ_BLOB)
 333                 die("blob expected in note %s for object %s",
 334                     sha1_to_hex(note), sha1_to_hex(obj));
 335         write_buf_to_worktree(obj, buf, size);
 336         free(buf);
 337 }
 338
 339 static int ll_merge_in_worktree(struct notes_merge_options *o,
 340                                 struct notes_merge_pair *p)
 341 {
 342         mmbuffer_t result_buf;
 343         mmfile_t base, local, remote;
 344         int status;
 345
 346         read_mmblob(&base, p->base);
 347         read_mmblob(&local, p->local);
 348         read_mmblob(&remote, p->remote);
 349
 350         status = ll_merge(&result_buf, sha1_to_hex(p->obj), &base, NULL,
 351                           &local, o->local_ref, &remote, o->remote_ref, NULL);
 352
 353         free(base.ptr);
 354         free(local.ptr);
 355         free(remote.ptr);
 356
 357         if ((status < 0) || !result_buf.ptr)
 358                 die("Failed to execute internal merge");
 359
 360         write_buf_to_worktree(p->obj, result_buf.ptr, result_buf.size);
 361         free(result_buf.ptr);
 362
 363         return status;
 364 }
 365
 366 static int merge_one_change_manual(struct notes_merge_options *o,
 367                                    struct notes_merge_pair *p,
 368                                    struct notes_tree *t)
 369 {
 370         const char *lref = o->local_ref ? o->local_ref : "local version";
 371         const char *rref = o->remote_ref ? o->remote_ref : "remote version";
 372
 373         trace_printf("\t\t\tmerge_one_change_manual(obj = %.7s, base = %.7s, "
 374                "local = %.7s, remote = %.7s)\n",
 375                sha1_to_hex(p->obj), sha1_to_hex(p->base),
 376                sha1_to_hex(p->local), sha1_to_hex(p->remote));
 377
 378         /* add "Conflicts:" section to commit message first time through */
 379         if (!o->has_worktree)
 380                 strbuf_addstr(&(o->commit_msg), "\n\nConflicts:\n");
 381
 382         strbuf_addf(&(o->commit_msg), "\t%s\n", sha1_to_hex(p->obj));
 383
 384         if (o->verbosity >= 2)
 385                 printf("Auto-merging notes for %s\n", sha1_to_hex(p->obj));
 386         check_notes_merge_worktree(o);
 387         if (is_null_sha1(p->local)) {
 388                 /* D/F conflict, checkout p->remote */
 389                 assert(!is_null_sha1(p->remote));
 390                 if (o->verbosity >= 1)
 391                         printf("CONFLICT (delete/modify): Notes for object %s "
 392                                 "deleted in %s and modified in %s. Version from %s "
 393                                 "left in tree.\n",
 394                                 sha1_to_hex(p->obj), lref, rref, rref);
 395                 write_note_to_worktree(p->obj, p->remote);
 396         } else if (is_null_sha1(p->remote)) {
 397                 /* D/F conflict, checkout p->local */
 398                 assert(!is_null_sha1(p->local));
 399                 if (o->verbosity >= 1)
 400                         printf("CONFLICT (delete/modify): Notes for object %s "
 401                                 "deleted in %s and modified in %s. Version from %s "
 402                                 "left in tree.\n",
 403                                 sha1_to_hex(p->obj), rref, lref, lref);
 404                 write_note_to_worktree(p->obj, p->local);
 405         } else {
 406                 /* "regular" conflict, checkout result of ll_merge() */
 407                 const char *reason = "content";
 408                 if (is_null_sha1(p->base))
 409                         reason = "add/add";
 410                 assert(!is_null_sha1(p->local));
 411                 assert(!is_null_sha1(p->remote));
 412                 if (o->verbosity >= 1)
 413                         printf("CONFLICT (%s): Merge conflict in notes for "
 414                                 "object %s\n", reason, sha1_to_hex(p->obj));
 415                 ll_merge_in_worktree(o, p);
 416         }
 417
 418         trace_printf("\t\t\tremoving from partial merge result\n");
 419         remove_note(t, p->obj);
 420
 421         return 1;
 422 }
 423
 424 static int merge_one_change(struct notes_merge_options *o,
 425                             struct notes_merge_pair *p, struct notes_tree *t)
 426 {
 427         /*
 428          * Return 0 if change is successfully resolved (stored in notes_tree).
 429          * Return 1 is change results in a conflict (NOT stored in notes_tree,
 430          * but instead written to NOTES_MERGE_WORKTREE with conflict markers).
 431          */
 432         switch (o->strategy) {
 433         case NOTES_MERGE_RESOLVE_MANUAL:
 434                 return merge_one_change_manual(o, p, t);
 435         case NOTES_MERGE_RESOLVE_OURS:
 436                 if (o->verbosity >= 2)
 437                         printf("Using local notes for %s\n",
 438                                                 sha1_to_hex(p->obj));
 439                 /* nothing to do */
 440                 return 0;
 441         case NOTES_MERGE_RESOLVE_THEIRS:
 442                 if (o->verbosity >= 2)
 443                         printf("Using remote notes for %s\n",
 444                                                 sha1_to_hex(p->obj));
 445                 if (add_note(t, p->obj, p->remote, combine_notes_overwrite))
 446                         die("BUG: combine_notes_overwrite failed");
 447                 return 0;
 448         case NOTES_MERGE_RESOLVE_UNION:
 449                 if (o->verbosity >= 2)
 450                         printf("Concatenating local and remote notes for %s\n",
 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                 if (o->verbosity >= 2)
 458                         printf("Concatenating unique lines in local and remote "
 459                                 "notes for %s\n", sha1_to_hex(p->obj));
 460                 if (add_note(t, p->obj, p->remote, combine_notes_cat_sort_uniq))
 461                         die("failed to concatenate notes "
 462                             "(combine_notes_cat_sort_uniq)");
 463                 return 0;
 464         }
 465         die("Unknown strategy (%i).", o->strategy);
 466 }
 467
 468 static int merge_changes(struct notes_merge_options *o,
 469                          struct notes_merge_pair *changes, int *num_changes,
 470                          struct notes_tree *t)
 471 {
 472         int i, conflicts = 0;
 473
 474         trace_printf("\tmerge_changes(num_changes = %i)\n", *num_changes);
 475         for (i = 0; i < *num_changes; i++) {
 476                 struct notes_merge_pair *p = changes + i;
 477                 trace_printf("\t\t%.7s: %.7s -> %.7s/%.7s\n",
 478                        sha1_to_hex(p->obj), sha1_to_hex(p->base),
 479                        sha1_to_hex(p->local), sha1_to_hex(p->remote));
 480
 481                 if (!hashcmp(p->base, p->remote)) {
 482                         /* no remote change; nothing to do */
 483                         trace_printf("\t\t\tskipping (no remote change)\n");
 484                 } else if (!hashcmp(p->local, p->remote)) {
 485                         /* same change in local and remote; nothing to do */
 486                         trace_printf("\t\t\tskipping (local == remote)\n");
 487                 } else if (!hashcmp(p->local, uninitialized) ||
 488                            !hashcmp(p->local, p->base)) {
 489                         /* no local change; adopt remote change */
 490                         trace_printf("\t\t\tno local change, adopted remote\n");
 491                         if (add_note(t, p->obj, p->remote,
 492                                      combine_notes_overwrite))
 493                                 die("BUG: combine_notes_overwrite failed");
 494                 } else {
 495                         /* need file-level merge between local and remote */
 496                         trace_printf("\t\t\tneed content-level merge\n");
 497                         conflicts += merge_one_change(o, p, t);
 498                 }
 499         }
 500
 501         return conflicts;
 502 }
 503
 504 static int merge_from_diffs(struct notes_merge_options *o,
 505                             const unsigned char *base,
 506                             const unsigned char *local,
 507                             const unsigned char *remote, struct notes_tree *t)
 508 {
 509         struct notes_merge_pair *changes;
 510         int num_changes, conflicts;
 511
 512         trace_printf("\tmerge_from_diffs(base = %.7s, local = %.7s, "
 513                "remote = %.7s)\n", sha1_to_hex(base), sha1_to_hex(local),
 514                sha1_to_hex(remote));
 515
 516         changes = diff_tree_remote(o, base, remote, &num_changes);
 517         diff_tree_local(o, changes, num_changes, base, local);
 518
 519         conflicts = merge_changes(o, changes, &num_changes, t);
 520         free(changes);
 521
 522         if (o->verbosity >= 4)
 523                 printf(t->dirty ?
 524                        "Merge result: %i unmerged notes and a dirty notes tree\n" :
 525                        "Merge result: %i unmerged notes and a clean notes tree\n",
 526                        conflicts);
 527
 528         return conflicts ? -1 : 1;
 529 }
 530
 531 int notes_merge(struct notes_merge_options *o,
 532                 struct notes_tree *local_tree,
 533                 unsigned char *result_sha1)
 534 {
 535         unsigned char local_sha1[20], remote_sha1[20];
 536         struct commit *local, *remote;
 537         struct commit_list *bases = NULL;
 538         const unsigned char *base_sha1, *base_tree_sha1;
 539         int result = 0;
 540
 541         assert(o->local_ref && o->remote_ref);
 542         assert(!strcmp(o->local_ref, local_tree->ref));
 543         hashclr(result_sha1);
 544
 545         trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
 546                o->local_ref, o->remote_ref);
 547
 548         /* Dereference o->local_ref into local_sha1 */
 549         if (read_ref_full(o->local_ref, 0, local_sha1, NULL))
 550                 die("Failed to resolve local notes ref '%s'", o->local_ref);
 551         else if (!check_refname_format(o->local_ref, 0) &&
 552                 is_null_sha1(local_sha1))
 553                 local = NULL; /* local_sha1 == null_sha1 indicates unborn ref */
 554         else if (!(local = lookup_commit_reference(local_sha1)))
 555                 die("Could not parse local commit %s (%s)",
 556                     sha1_to_hex(local_sha1), o->local_ref);
 557         trace_printf("\tlocal commit: %.7s\n", sha1_to_hex(local_sha1));
 558
 559         /* Dereference o->remote_ref into remote_sha1 */
 560         if (get_sha1(o->remote_ref, remote_sha1)) {
 561                 /*
 562                  * Failed to get remote_sha1. If o->remote_ref looks like an
 563                  * unborn ref, perform the merge using an empty notes tree.
 564                  */
 565                 if (!check_refname_format(o->remote_ref, 0)) {
 566                         hashclr(remote_sha1);
 567                         remote = NULL;
 568                 } else {
 569                         die("Failed to resolve remote notes ref '%s'",
 570                             o->remote_ref);
 571                 }
 572         } else if (!(remote = lookup_commit_reference(remote_sha1))) {
 573                 die("Could not parse remote commit %s (%s)",
 574                     sha1_to_hex(remote_sha1), o->remote_ref);
 575         }
 576         trace_printf("\tremote commit: %.7s\n", sha1_to_hex(remote_sha1));
 577
 578         if (!local && !remote)
 579                 die("Cannot merge empty notes ref (%s) into empty notes ref "
 580                     "(%s)", o->remote_ref, o->local_ref);
 581         if (!local) {
 582                 /* result == remote commit */
 583                 hashcpy(result_sha1, remote_sha1);
 584                 goto found_result;
 585         }
 586         if (!remote) {
 587                 /* result == local commit */
 588                 hashcpy(result_sha1, local_sha1);
 589                 goto found_result;
 590         }
 591         assert(local && remote);
 592
 593         /* Find merge bases */
 594         bases = get_merge_bases(local, remote);
 595         if (!bases) {
 596                 base_sha1 = null_sha1;
 597                 base_tree_sha1 = EMPTY_TREE_SHA1_BIN;
 598                 if (o->verbosity >= 4)
 599                         printf("No merge base found; doing history-less merge\n");
 600         } else if (!bases->next) {
 601                 base_sha1 = bases->item->object.oid.hash;
 602                 base_tree_sha1 = bases->item->tree->object.oid.hash;
 603                 if (o->verbosity >= 4)
 604                         printf("One merge base found (%.7s)\n",
 605                                 sha1_to_hex(base_sha1));
 606         } else {
 607                 /* TODO: How to handle multiple merge-bases? */
 608                 base_sha1 = bases->item->object.oid.hash;
 609                 base_tree_sha1 = bases->item->tree->object.oid.hash;
 610                 if (o->verbosity >= 3)
 611                         printf("Multiple merge bases found. Using the first "
 612                                 "(%.7s)\n", sha1_to_hex(base_sha1));
 613         }
 614
 615         if (o->verbosity >= 4)
 616                 printf("Merging remote commit %.7s into local commit %.7s with "
 617                         "merge-base %.7s\n", oid_to_hex(&remote->object.oid),
 618                         oid_to_hex(&local->object.oid),
 619                         sha1_to_hex(base_sha1));
 620
 621         if (!hashcmp(remote->object.oid.hash, base_sha1)) {
 622                 /* Already merged; result == local commit */
 623                 if (o->verbosity >= 2)
 624                         printf("Already up-to-date!\n");
 625                 hashcpy(result_sha1, local->object.oid.hash);
 626                 goto found_result;
 627         }
 628         if (!hashcmp(local->object.oid.hash, base_sha1)) {
 629                 /* Fast-forward; result == remote commit */
 630                 if (o->verbosity >= 2)
 631                         printf("Fast-forward\n");
 632                 hashcpy(result_sha1, remote->object.oid.hash);
 633                 goto found_result;
 634         }
 635
 636         result = merge_from_diffs(o, base_tree_sha1, local->tree->object.oid.hash,
 637                                   remote->tree->object.oid.hash, local_tree);
 638
 639         if (result != 0) { /* non-trivial merge (with or without conflicts) */
 640                 /* Commit (partial) result */
 641                 struct commit_list *parents = NULL;
 642                 commit_list_insert(remote, &parents); /* LIFO order */
 643                 commit_list_insert(local, &parents);
 644                 create_notes_commit(local_tree, parents,
 645                                     o->commit_msg.buf, o->commit_msg.len,
 646                                     result_sha1);
 647         }
 648
 649 found_result:
 650         free_commit_list(bases);
 651         strbuf_release(&(o->commit_msg));
 652         trace_printf("notes_merge(): result = %i, result_sha1 = %.7s\n",
 653                result, sha1_to_hex(result_sha1));
 654         return result;
 655 }
 656
 657 int notes_merge_commit(struct notes_merge_options *o,
 658                        struct notes_tree *partial_tree,
 659                        struct commit *partial_commit,
 660                        unsigned char *result_sha1)
 661 {
 662         /*
 663          * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
 664          * found notes to 'partial_tree'. Write the updated notes tree to
 665          * the DB, and commit the resulting tree object while reusing the
 666          * commit message and parents from 'partial_commit'.
 667          * Finally store the new commit object SHA1 into 'result_sha1'.
 668          */
 669         DIR *dir;
 670         struct dirent *e;
 671         struct strbuf path = STRBUF_INIT;
 672         const char *buffer = get_commit_buffer(partial_commit, NULL);
 673         const char *msg = strstr(buffer, "\n\n");
 674         int baselen;
 675
 676         strbuf_addstr(&path, git_path(NOTES_MERGE_WORKTREE));
 677         if (o->verbosity >= 3)
 678                 printf("Committing notes in notes merge worktree at %s\n",
 679                         path.buf);
 680
 681         if (!msg || msg[2] == '\0')
 682                 die("partial notes commit has empty message");
 683         msg += 2;
 684
 685         dir = opendir(path.buf);
 686         if (!dir)
 687                 die_errno("could not open %s", path.buf);
 688
 689         strbuf_addch(&path, '/');
 690         baselen = path.len;
 691         while ((e = readdir(dir)) != NULL) {
 692                 struct stat st;
 693                 unsigned char obj_sha1[20], blob_sha1[20];
 694
 695                 if (is_dot_or_dotdot(e->d_name))
 696                         continue;
 697
 698                 if (strlen(e->d_name) != 40 || get_sha1_hex(e->d_name, obj_sha1)) {
 699                         if (o->verbosity >= 3)
 700                                 printf("Skipping non-SHA1 entry '%s%s'\n",
 701                                         path.buf, e->d_name);
 702                         continue;
 703                 }
 704
 705                 strbuf_addstr(&path, e->d_name);
 706                 /* write file as blob, and add to partial_tree */
 707                 if (stat(path.buf, &st))
 708                         die_errno("Failed to stat '%s'", path.buf);
 709                 if (index_path(blob_sha1, path.buf, &st, HASH_WRITE_OBJECT))
 710                         die("Failed to write blob object from '%s'", path.buf);
 711                 if (add_note(partial_tree, obj_sha1, blob_sha1, NULL))
 712                         die("Failed to add resolved note '%s' to notes tree",
 713                             path.buf);
 714                 if (o->verbosity >= 4)
 715                         printf("Added resolved note for object %s: %s\n",
 716                                 sha1_to_hex(obj_sha1), sha1_to_hex(blob_sha1));
 717                 strbuf_setlen(&path, baselen);
 718         }
 719
 720         create_notes_commit(partial_tree, partial_commit->parents,
 721                             msg, strlen(msg), result_sha1);
 722         unuse_commit_buffer(partial_commit, buffer);
 723         if (o->verbosity >= 4)
 724                 printf("Finalized notes merge commit: %s\n",
 725                         sha1_to_hex(result_sha1));
 726         strbuf_release(&path);
 727         closedir(dir);
 728         return 0;
 729 }
 730
 731 int notes_merge_abort(struct notes_merge_options *o)
 732 {
 733         /*
 734          * Remove all files within .git/NOTES_MERGE_WORKTREE. We do not remove
 735          * the .git/NOTES_MERGE_WORKTREE directory itself, since it might be
 736          * the current working directory of the user.
 737          */
 738         struct strbuf buf = STRBUF_INIT;
 739         int ret;
 740
 741         strbuf_addstr(&buf, git_path(NOTES_MERGE_WORKTREE));
 742         if (o->verbosity >= 3)
 743                 printf("Removing notes merge worktree at %s/*\n", buf.buf);
 744         ret = remove_dir_recursively(&buf, REMOVE_DIR_KEEP_TOPLEVEL);
 745         strbuf_release(&buf);
 746         return ret;
 747 }