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_sha1(p->one->sha1));
  45                 assert(!is_null_sha1(p->two->sha1));
  46                 break;
  47         case DIFF_STATUS_ADDED:
  48                 assert(is_null_sha1(p->one->sha1));
  49                 break;
  50         case DIFF_STATUS_DELETED:
  51                 assert(is_null_sha1(p->two->sha1));
  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, 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         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, sha1_to_hex(p->one->sha1),
 207                                sha1_to_hex(p->two->sha1));
 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                                sha1_to_hex(p->one->sha1),
 215                                sha1_to_hex(p->two->sha1));
 216                         continue;
 217                 }
 218
 219                 assert(!hashcmp(mp->obj, obj));
 220                 if (is_null_sha1(p->two->sha1)) { /* 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_sha1(p->one->sha1)) { /* 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->sha1);
 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->sha1, mp->base));
 251                         assert(!hashcmp(mp->local, uninitialized));
 252                         hashcpy(mp->local, p->two->sha1);
 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         diff_tree_release_paths(&opt);
 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(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(t->dirty ?
 527                        "Merge result: %i unmerged notes and a dirty notes tree\n" :
 528                        "Merge result: %i unmerged notes and a clean notes tree\n",
 529                        conflicts);
 530
 531         return conflicts ? -1 : 1;
 532 }
 533
 534 int notes_merge(struct notes_merge_options *o,
 535                 struct notes_tree *local_tree,
 536                 unsigned char *result_sha1)
 537 {
 538         unsigned char local_sha1[20], remote_sha1[20];
 539         struct commit *local, *remote;
 540         struct commit_list *bases = NULL;
 541         const unsigned char *base_sha1, *base_tree_sha1;
 542         int result = 0;
 543
 544         assert(o->local_ref && o->remote_ref);
 545         assert(!strcmp(o->local_ref, local_tree->ref));
 546         hashclr(result_sha1);
 547
 548         trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
 549                o->local_ref, o->remote_ref);
 550
 551         /* Dereference o->local_ref into local_sha1 */
 552         if (read_ref_full(o->local_ref, local_sha1, 0, NULL))
 553                 die("Failed to resolve local notes ref '%s'", o->local_ref);
 554         else if (!check_refname_format(o->local_ref, 0) &&
 555                 is_null_sha1(local_sha1))
 556                 local = NULL; /* local_sha1 == null_sha1 indicates unborn ref */
 557         else if (!(local = lookup_commit_reference(local_sha1)))
 558                 die("Could not parse local commit %s (%s)",
 559                     sha1_to_hex(local_sha1), o->local_ref);
 560         trace_printf("\tlocal commit: %.7s\n", sha1_to_hex(local_sha1));
 561
 562         /* Dereference o->remote_ref into remote_sha1 */
 563         if (get_sha1(o->remote_ref, remote_sha1)) {
 564                 /*
 565                  * Failed to get remote_sha1. If o->remote_ref looks like an
 566                  * unborn ref, perform the merge using an empty notes tree.
 567                  */
 568                 if (!check_refname_format(o->remote_ref, 0)) {
 569                         hashclr(remote_sha1);
 570                         remote = NULL;
 571                 } else {
 572                         die("Failed to resolve remote notes ref '%s'",
 573                             o->remote_ref);
 574                 }
 575         } else if (!(remote = lookup_commit_reference(remote_sha1))) {
 576                 die("Could not parse remote commit %s (%s)",
 577                     sha1_to_hex(remote_sha1), o->remote_ref);
 578         }
 579         trace_printf("\tremote commit: %.7s\n", sha1_to_hex(remote_sha1));
 580
 581         if (!local && !remote)
 582                 die("Cannot merge empty notes ref (%s) into empty notes ref "
 583                     "(%s)", o->remote_ref, o->local_ref);
 584         if (!local) {
 585                 /* result == remote commit */
 586                 hashcpy(result_sha1, remote_sha1);
 587                 goto found_result;
 588         }
 589         if (!remote) {
 590                 /* result == local commit */
 591                 hashcpy(result_sha1, local_sha1);
 592                 goto found_result;
 593         }
 594         assert(local && remote);
 595
 596         /* Find merge bases */
 597         bases = get_merge_bases(local, remote, 1);
 598         if (!bases) {
 599                 base_sha1 = null_sha1;
 600                 base_tree_sha1 = EMPTY_TREE_SHA1_BIN;
 601                 if (o->verbosity >= 4)
 602                         printf("No merge base found; doing history-less merge\n");
 603         } else if (!bases->next) {
 604                 base_sha1 = bases->item->object.sha1;
 605                 base_tree_sha1 = bases->item->tree->object.sha1;
 606                 if (o->verbosity >= 4)
 607                         printf("One merge base found (%.7s)\n",
 608                                 sha1_to_hex(base_sha1));
 609         } else {
 610                 /* TODO: How to handle multiple merge-bases? */
 611                 base_sha1 = bases->item->object.sha1;
 612                 base_tree_sha1 = bases->item->tree->object.sha1;
 613                 if (o->verbosity >= 3)
 614                         printf("Multiple merge bases found. Using the first "
 615                                 "(%.7s)\n", sha1_to_hex(base_sha1));
 616         }
 617
 618         if (o->verbosity >= 4)
 619                 printf("Merging remote commit %.7s into local commit %.7s with "
 620                         "merge-base %.7s\n", sha1_to_hex(remote->object.sha1),
 621                         sha1_to_hex(local->object.sha1),
 622                         sha1_to_hex(base_sha1));
 623
 624         if (!hashcmp(remote->object.sha1, base_sha1)) {
 625                 /* Already merged; result == local commit */
 626                 if (o->verbosity >= 2)
 627                         printf("Already up-to-date!\n");
 628                 hashcpy(result_sha1, local->object.sha1);
 629                 goto found_result;
 630         }
 631         if (!hashcmp(local->object.sha1, base_sha1)) {
 632                 /* Fast-forward; result == remote commit */
 633                 if (o->verbosity >= 2)
 634                         printf("Fast-forward\n");
 635                 hashcpy(result_sha1, remote->object.sha1);
 636                 goto found_result;
 637         }
 638
 639         result = merge_from_diffs(o, base_tree_sha1, local->tree->object.sha1,
 640                                   remote->tree->object.sha1, local_tree);
 641
 642         if (result != 0) { /* non-trivial merge (with or without conflicts) */
 643                 /* Commit (partial) result */
 644                 struct commit_list *parents = NULL;
 645                 commit_list_insert(remote, &parents); /* LIFO order */
 646                 commit_list_insert(local, &parents);
 647                 create_notes_commit(local_tree, parents, &o->commit_msg,
 648                                     result_sha1);
 649         }
 650
 651 found_result:
 652         free_commit_list(bases);
 653         strbuf_release(&(o->commit_msg));
 654         trace_printf("notes_merge(): result = %i, result_sha1 = %.7s\n",
 655                result, sha1_to_hex(result_sha1));
 656         return result;
 657 }
 658
 659 int notes_merge_commit(struct notes_merge_options *o,
 660                        struct notes_tree *partial_tree,
 661                        struct commit *partial_commit,
 662                        unsigned char *result_sha1)
 663 {
 664         /*
 665          * Iterate through files in .git/NOTES_MERGE_WORKTREE and add all
 666          * found notes to 'partial_tree'. Write the updated notes tree to
 667          * the DB, and commit the resulting tree object while reusing the
 668          * commit message and parents from 'partial_commit'.
 669          * Finally store the new commit object SHA1 into 'result_sha1'.
 670          */
 671         DIR *dir;
 672         struct dirent *e;
 673         struct strbuf path = STRBUF_INIT;
 674         char *msg = strstr(partial_commit->buffer, "\n\n");
 675         struct strbuf sb_msg = STRBUF_INIT;
 676         int baselen;
 677
 678         strbuf_addstr(&path, git_path(NOTES_MERGE_WORKTREE));
 679         if (o->verbosity >= 3)
 680                 printf("Committing notes in notes merge worktree at %s\n",
 681                         path.buf);
 682
 683         if (!msg || msg[2] == '\0')
 684                 die("partial notes commit has empty message");
 685         msg += 2;
 686
 687         dir = opendir(path.buf);
 688         if (!dir)
 689                 die_errno("could not open %s", path.buf);
 690
 691         strbuf_addch(&path, '/');
 692         baselen = path.len;
 693         while ((e = readdir(dir)) != NULL) {
 694                 struct stat st;
 695                 unsigned char obj_sha1[20], blob_sha1[20];
 696
 697                 if (is_dot_or_dotdot(e->d_name))
 698                         continue;
 699
 700                 if (strlen(e->d_name) != 40 || get_sha1_hex(e->d_name, obj_sha1)) {
 701                         if (o->verbosity >= 3)
 702                                 printf("Skipping non-SHA1 entry '%s%s'\n",
 703                                         path.buf, e->d_name);
 704                         continue;
 705                 }
 706
 707                 strbuf_addstr(&path, e->d_name);
 708                 /* write file as blob, and add to partial_tree */
 709                 if (stat(path.buf, &st))
 710                         die_errno("Failed to stat '%s'", path.buf);
 711                 if (index_path(blob_sha1, path.buf, &st, HASH_WRITE_OBJECT))
 712                         die("Failed to write blob object from '%s'", path.buf);
 713                 if (add_note(partial_tree, obj_sha1, blob_sha1, NULL))
 714                         die("Failed to add resolved note '%s' to notes tree",
 715                             path.buf);
 716                 if (o->verbosity >= 4)
 717                         printf("Added resolved note for object %s: %s\n",
 718                                 sha1_to_hex(obj_sha1), sha1_to_hex(blob_sha1));
 719                 strbuf_setlen(&path, baselen);
 720         }
 721
 722         strbuf_attach(&sb_msg, msg, strlen(msg), strlen(msg) + 1);
 723         create_notes_commit(partial_tree, partial_commit->parents, &sb_msg,
 724                             result_sha1);
 725         if (o->verbosity >= 4)
 726                 printf("Finalized notes merge commit: %s\n",
 727                         sha1_to_hex(result_sha1));
 728         strbuf_release(&path);
 729         closedir(dir);
 730         return 0;
 731 }
 732
 733 int notes_merge_abort(struct notes_merge_options *o)
 734 {
 735         /*
 736          * Remove all files within .git/NOTES_MERGE_WORKTREE. We do not remove
 737          * the .git/NOTES_MERGE_WORKTREE directory itself, since it might be
 738          * the current working directory of the user.
 739          */
 740         struct strbuf buf = STRBUF_INIT;
 741         int ret;
 742
 743         strbuf_addstr(&buf, git_path(NOTES_MERGE_WORKTREE));
 744         if (o->verbosity >= 3)
 745                 printf("Removing notes merge worktree at %s/*\n", buf.buf);
 746         ret = remove_dir_recursively(&buf, REMOVE_DIR_KEEP_TOPLEVEL);
 747         strbuf_release(&buf);
 748         return ret;
 749 }