read-tree.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6 #define DBRT_DEBUG 1
   7
   8 #include "cache.h"
   9
  10 #include "object.h"
  11 #include "tree.h"
  12
  13 static int merge = 0;
  14 static int update = 0;
  15 static int index_only = 0;
  16 static int nontrivial_merge = 0;
  17 static int trivial_merges_only = 0;
  18 static int aggressive = 0;
  19
  20 static int head_idx = -1;
  21 static int merge_size = 0;
  22
  23 static struct object_list *trees = NULL;
  24
  25 static struct cache_entry df_conflict_entry = {
  26 };
  27
  28 static struct tree_entry_list df_conflict_list = {
  29         .name = NULL,
  30         .next = &df_conflict_list
  31 };
  32
  33 typedef int (*merge_fn_t)(struct cache_entry **src);
  34
  35 static int entcmp(char *name1, int dir1, char *name2, int dir2)
  36 {
  37         int len1 = strlen(name1);
  38         int len2 = strlen(name2);
  39         int len = len1 < len2 ? len1 : len2;
  40         int ret = memcmp(name1, name2, len);
  41         unsigned char c1, c2;
  42         if (ret)
  43                 return ret;
  44         c1 = name1[len];
  45         c2 = name2[len];
  46         if (!c1 && dir1)
  47                 c1 = '/';
  48         if (!c2 && dir2)
  49                 c2 = '/';
  50         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  51         if (c1 && c2 && !ret)
  52                 ret = len1 - len2;
  53         return ret;
  54 }
  55
  56 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
  57                             const char *base, merge_fn_t fn, int *indpos)
  58 {
  59         int baselen = strlen(base);
  60         int src_size = len + 1;
  61         do {
  62                 int i;
  63                 char *first;
  64                 int firstdir = 0;
  65                 int pathlen;
  66                 unsigned ce_size;
  67                 struct tree_entry_list **subposns;
  68                 struct cache_entry **src;
  69                 int any_files = 0;
  70                 int any_dirs = 0;
  71                 char *cache_name;
  72                 int ce_stage;
  73
  74                 /* Find the first name in the input. */
  75
  76                 first = NULL;
  77                 cache_name = NULL;
  78
  79                 /* Check the cache */
  80                 if (merge && *indpos < active_nr) {
  81                         /* This is a bit tricky: */
  82                         /* If the index has a subdirectory (with
  83                          * contents) as the first name, it'll get a
  84                          * filename like "foo/bar". But that's after
  85                          * "foo", so the entry in trees will get
  86                          * handled first, at which point we'll go into
  87                          * "foo", and deal with "bar" from the index,
  88                          * because the base will be "foo/". The only
  89                          * way we can actually have "foo/bar" first of
  90                          * all the things is if the trees don't
  91                          * contain "foo" at all, in which case we'll
  92                          * handle "foo/bar" without going into the
  93                          * directory, but that's fine (and will return
  94                          * an error anyway, with the added unknown
  95                          * file case.
  96                          */
  97
  98                         cache_name = active_cache[*indpos]->name;
  99                         if (strlen(cache_name) > baselen &&
 100                             !memcmp(cache_name, base, baselen)) {
 101                                 cache_name += baselen;
 102                                 first = cache_name;
 103                         } else {
 104                                 cache_name = NULL;
 105                         }
 106                 }
 107
 108 #if DBRT_DEBUG > 1
 109                 if (first)
 110                         printf("index %s\n", first);
 111 #endif
 112                 for (i = 0; i < len; i++) {
 113                         if (!posns[i] || posns[i] == &df_conflict_list)
 114                                 continue;
 115 #if DBRT_DEBUG > 1
 116                         printf("%d %s\n", i + 1, posns[i]->name);
 117 #endif
 118                         if (!first || entcmp(first, firstdir,
 119                                              posns[i]->name,
 120                                              posns[i]->directory) > 0) {
 121                                 first = posns[i]->name;
 122                                 firstdir = posns[i]->directory;
 123                         }
 124                 }
 125                 /* No name means we're done */
 126                 if (!first)
 127                         return 0;
 128
 129                 pathlen = strlen(first);
 130                 ce_size = cache_entry_size(baselen + pathlen);
 131
 132                 src = xmalloc(sizeof(struct cache_entry *) * src_size);
 133                 memset(src, 0, sizeof(struct cache_entry *) * src_size);
 134
 135                 subposns = xmalloc(sizeof(struct tree_list_entry *) * len);
 136                 memset(subposns, 0, sizeof(struct tree_list_entry *) * len);
 137
 138                 if (cache_name && !strcmp(cache_name, first)) {
 139                         any_files = 1;
 140                         src[0] = active_cache[*indpos];
 141                         remove_cache_entry_at(*indpos);
 142                 }
 143
 144                 for (i = 0; i < len; i++) {
 145                         struct cache_entry *ce;
 146
 147                         if (!posns[i] ||
 148                             (posns[i] != &df_conflict_list &&
 149                              strcmp(first, posns[i]->name))) {
 150                                 continue;
 151                         }
 152
 153                         if (posns[i] == &df_conflict_list) {
 154                                 src[i + merge] = &df_conflict_entry;
 155                                 continue;
 156                         }
 157
 158                         if (posns[i]->directory) {
 159                                 any_dirs = 1;
 160                                 parse_tree(posns[i]->item.tree);
 161                                 subposns[i] = posns[i]->item.tree->entries;
 162                                 posns[i] = posns[i]->next;
 163                                 src[i + merge] = &df_conflict_entry;
 164                                 continue;
 165                         }
 166
 167                         if (!merge)
 168                                 ce_stage = 0;
 169                         else if (i + 1 < head_idx)
 170                                 ce_stage = 1;
 171                         else if (i + 1 > head_idx)
 172                                 ce_stage = 3;
 173                         else
 174                                 ce_stage = 2;
 175
 176                         ce = xmalloc(ce_size);
 177                         memset(ce, 0, ce_size);
 178                         ce->ce_mode = create_ce_mode(posns[i]->mode);
 179                         ce->ce_flags = create_ce_flags(baselen + pathlen,
 180                                                        ce_stage);
 181                         memcpy(ce->name, base, baselen);
 182                         memcpy(ce->name + baselen, first, pathlen + 1);
 183
 184                         any_files = 1;
 185
 186                         memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
 187                         src[i + merge] = ce;
 188                         subposns[i] = &df_conflict_list;
 189                         posns[i] = posns[i]->next;
 190                 }
 191                 if (any_files) {
 192                         if (merge) {
 193                                 int ret;
 194
 195 #if DBRT_DEBUG > 1
 196                                 printf("%s:\n", first);
 197                                 for (i = 0; i < src_size; i++) {
 198                                         printf(" %d ", i);
 199                                         if (src[i])
 200                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
 201                                         else
 202                                                 printf("\n");
 203                                 }
 204 #endif
 205                                 ret = fn(src);
 206
 207 #if DBRT_DEBUG > 1
 208                                 printf("Added %d entries\n", ret);
 209 #endif
 210                                 *indpos += ret;
 211                         } else {
 212                                 for (i = 0; i < src_size; i++) {
 213                                         if (src[i]) {
 214                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 215                                         }
 216                                 }
 217                         }
 218                 }
 219                 if (any_dirs) {
 220                         char *newbase = xmalloc(baselen + 2 + pathlen);
 221                         memcpy(newbase, base, baselen);
 222                         memcpy(newbase + baselen, first, pathlen);
 223                         newbase[baselen + pathlen] = '/';
 224                         newbase[baselen + pathlen + 1] = '\0';
 225                         if (unpack_trees_rec(subposns, len, newbase, fn,
 226                                              indpos))
 227                                 return -1;
 228                         free(newbase);
 229                 }
 230                 free(subposns);
 231                 free(src);
 232         } while (1);
 233 }
 234
 235 static void reject_merge(struct cache_entry *ce)
 236 {
 237         die("Entry '%s' would be overwritten by merge. Cannot merge.",
 238             ce->name);
 239 }
 240
 241 /* Unlink the last component and attempt to remove leading
 242  * directories, in case this unlink is the removal of the
 243  * last entry in the directory -- empty directories are removed.
 244  */
 245 static void unlink_entry(char *name)
 246 {
 247         char *cp, *prev;
 248
 249         if (unlink(name))
 250                 return;
 251         prev = NULL;
 252         while (1) {
 253                 int status;
 254                 cp = strrchr(name, '/');
 255                 if (prev)
 256                         *prev = '/';
 257                 if (!cp)
 258                         break;
 259
 260                 *cp = 0;
 261                 status = rmdir(name);
 262                 if (status) {
 263                         *cp = '/';
 264                         break;
 265                 }
 266                 prev = cp;
 267         }
 268 }
 269
 270 static void check_updates(struct cache_entry **src, int nr)
 271 {
 272         static struct checkout state = {
 273                 .base_dir = "",
 274                 .force = 1,
 275                 .quiet = 1,
 276                 .refresh_cache = 1,
 277         };
 278         unsigned short mask = htons(CE_UPDATE);
 279         while (nr--) {
 280                 struct cache_entry *ce = *src++;
 281                 if (!ce->ce_mode) {
 282                         if (update)
 283                                 unlink_entry(ce->name);
 284                         continue;
 285                 }
 286                 if (ce->ce_flags & mask) {
 287                         ce->ce_flags &= ~mask;
 288                         if (update)
 289                                 checkout_entry(ce, &state);
 290                 }
 291         }
 292 }
 293
 294 static int unpack_trees(merge_fn_t fn)
 295 {
 296         int indpos = 0;
 297         unsigned len = object_list_length(trees);
 298         struct tree_entry_list **posns;
 299         int i;
 300         struct object_list *posn = trees;
 301         merge_size = len;
 302
 303         if (len) {
 304                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
 305                 for (i = 0; i < len; i++) {
 306                         posns[i] = ((struct tree *) posn->item)->entries;
 307                         posn = posn->next;
 308                 }
 309                 if (unpack_trees_rec(posns, len, "", fn, &indpos))
 310                         return -1;
 311         }
 312
 313         if (trivial_merges_only && nontrivial_merge)
 314                 die("Merge requires file-level merging");
 315
 316         check_updates(active_cache, active_nr);
 317         return 0;
 318 }
 319
 320 static int list_tree(unsigned char *sha1)
 321 {
 322         struct tree *tree = parse_tree_indirect(sha1);
 323         if (!tree)
 324                 return -1;
 325         object_list_append(&tree->object, &trees);
 326         return 0;
 327 }
 328
 329 static int same(struct cache_entry *a, struct cache_entry *b)
 330 {
 331         if (!!a != !!b)
 332                 return 0;
 333         if (!a && !b)
 334                 return 1;
 335         return a->ce_mode == b->ce_mode &&
 336                 !memcmp(a->sha1, b->sha1, 20);
 337 }
 338
 339
 340 /*
 341  * When a CE gets turned into an unmerged entry, we
 342  * want it to be up-to-date
 343  */
 344 static void verify_uptodate(struct cache_entry *ce)
 345 {
 346         struct stat st;
 347
 348         if (index_only)
 349                 return;
 350
 351         if (!lstat(ce->name, &st)) {
 352                 unsigned changed = ce_match_stat(ce, &st);
 353                 if (!changed)
 354                         return;
 355                 errno = 0;
 356         }
 357         if (errno == ENOENT)
 358                 return;
 359         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 360 }
 361
 362 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 363 {
 364         merge->ce_flags |= htons(CE_UPDATE);
 365         if (old) {
 366                 /*
 367                  * See if we can re-use the old CE directly?
 368                  * That way we get the uptodate stat info.
 369                  *
 370                  * This also removes the UPDATE flag on
 371                  * a match.
 372                  */
 373                 if (same(old, merge)) {
 374                         *merge = *old;
 375                 } else {
 376                         verify_uptodate(old);
 377                 }
 378         }
 379         merge->ce_flags &= ~htons(CE_STAGEMASK);
 380         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 381         return 1;
 382 }
 383
 384 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 385 {
 386         if (old)
 387                 verify_uptodate(old);
 388         ce->ce_mode = 0;
 389         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 390         return 1;
 391 }
 392
 393 static int keep_entry(struct cache_entry *ce)
 394 {
 395         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 396         return 1;
 397 }
 398
 399 #if DBRT_DEBUG
 400 static void show_stage_entry(FILE *o,
 401                              const char *label, const struct cache_entry *ce)
 402 {
 403         if (!ce)
 404                 fprintf(o, "%s (missing)\n", label);
 405         else
 406                 fprintf(o, "%s%06o %s %d\t%s\n",
 407                         label,
 408                         ntohl(ce->ce_mode),
 409                         sha1_to_hex(ce->sha1),
 410                         ce_stage(ce),
 411                         ce->name);
 412 }
 413 #endif
 414
 415 static int threeway_merge(struct cache_entry **stages)
 416 {
 417         struct cache_entry *index;
 418         struct cache_entry *head;
 419         struct cache_entry *remote = stages[head_idx + 1];
 420         int count;
 421         int head_match = 0;
 422         int remote_match = 0;
 423
 424         int df_conflict_head = 0;
 425         int df_conflict_remote = 0;
 426
 427         int any_anc_missing = 0;
 428         int no_anc_exists = 1;
 429         int i;
 430
 431         for (i = 1; i < head_idx; i++) {
 432                 if (!stages[i])
 433                         any_anc_missing = 1;
 434                 else
 435                         no_anc_exists = 0;
 436         }
 437
 438         index = stages[0];
 439         head = stages[head_idx];
 440
 441         if (head == &df_conflict_entry) {
 442                 df_conflict_head = 1;
 443                 head = NULL;
 444         }
 445
 446         if (remote == &df_conflict_entry) {
 447                 df_conflict_remote = 1;
 448                 remote = NULL;
 449         }
 450
 451         /* First, if there's a #16 situation, note that to prevent #13
 452          * and #14.
 453          */
 454         if (!same(remote, head)) {
 455                 for (i = 1; i < head_idx; i++) {
 456                         if (same(stages[i], head)) {
 457                                 head_match = i;
 458                         }
 459                         if (same(stages[i], remote)) {
 460                                 remote_match = i;
 461                         }
 462                 }
 463         }
 464
 465         /* We start with cases where the index is allowed to match
 466          * something other than the head: #14(ALT) and #2ALT, where it
 467          * is permitted to match the result instead.
 468          */
 469         /* #14, #14ALT, #2ALT */
 470         if (remote && !df_conflict_head && head_match && !remote_match) {
 471                 if (index && !same(index, remote) && !same(index, head))
 472                         reject_merge(index);
 473                 return merged_entry(remote, index);
 474         }
 475         /*
 476          * If we have an entry in the index cache, then we want to
 477          * make sure that it matches head.
 478          */
 479         if (index && !same(index, head)) {
 480                 reject_merge(index);
 481         }
 482
 483         if (head) {
 484                 /* #5ALT, #15 */
 485                 if (same(head, remote))
 486                         return merged_entry(head, index);
 487                 /* #13, #3ALT */
 488                 if (!df_conflict_remote && remote_match && !head_match)
 489                         return merged_entry(head, index);
 490         }
 491
 492         /* #1 */
 493         if (!head && !remote && any_anc_missing)
 494                 return 0;
 495
 496         /* Under the new "aggressive" rule, we resolve mostly trivial
 497          * cases that we historically had git-merge-one-file resolve.
 498          */
 499         if (aggressive) {
 500                 int head_deleted = !head && !df_conflict_head;
 501                 int remote_deleted = !remote && !df_conflict_remote;
 502                 /*
 503                  * Deleted in both.
 504                  * Deleted in one and unchanged in the other.
 505                  */
 506                 if ((head_deleted && remote_deleted) ||
 507                     (head_deleted && remote && remote_match) ||
 508                     (remote_deleted && head && head_match))
 509                         return 0;
 510
 511                 /*
 512                  * Added in both, identically.
 513                  */
 514                 if (no_anc_exists && head && remote && same(head, remote))
 515                         return merged_entry(head, index);
 516
 517         }
 518
 519         /* Below are "no merge" cases, which require that the index be
 520          * up-to-date to avoid the files getting overwritten with
 521          * conflict resolution files.
 522          */
 523         if (index) {
 524                 verify_uptodate(index);
 525         }
 526
 527         nontrivial_merge = 1;
 528
 529         /* #2, #3, #4, #6, #7, #9, #11. */
 530         count = 0;
 531         if (!head_match || !remote_match) {
 532                 for (i = 1; i < head_idx; i++) {
 533                         if (stages[i]) {
 534                                 keep_entry(stages[i]);
 535                                 count++;
 536                                 break;
 537                         }
 538                 }
 539         }
 540 #if DBRT_DEBUG
 541         else {
 542                 fprintf(stderr, "read-tree: warning #16 detected\n");
 543                 show_stage_entry(stderr, "head   ", stages[head_match]);
 544                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 545         }
 546 #endif
 547         if (head) { count += keep_entry(head); }
 548         if (remote) { count += keep_entry(remote); }
 549         return count;
 550 }
 551
 552 /*
 553  * Two-way merge.
 554  *
 555  * The rule is to "carry forward" what is in the index without losing
 556  * information across a "fast forward", favoring a successful merge
 557  * over a merge failure when it makes sense.  For details of the
 558  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 559  *
 560  */
 561 static int twoway_merge(struct cache_entry **src)
 562 {
 563         struct cache_entry *current = src[0];
 564         struct cache_entry *oldtree = src[1], *newtree = src[2];
 565
 566         if (merge_size != 2)
 567                 return error("Cannot do a twoway merge of %d trees\n",
 568                              merge_size);
 569
 570         if (current) {
 571                 if ((!oldtree && !newtree) || /* 4 and 5 */
 572                     (!oldtree && newtree &&
 573                      same(current, newtree)) || /* 6 and 7 */
 574                     (oldtree && newtree &&
 575                      same(oldtree, newtree)) || /* 14 and 15 */
 576                     (oldtree && newtree &&
 577                      !same(oldtree, newtree) && /* 18 and 19*/
 578                      same(current, newtree))) {
 579                         return keep_entry(current);
 580                 }
 581                 else if (oldtree && !newtree && same(current, oldtree)) {
 582                         /* 10 or 11 */
 583                         return deleted_entry(oldtree, current);
 584                 }
 585                 else if (oldtree && newtree &&
 586                          same(current, oldtree) && !same(current, newtree)) {
 587                         /* 20 or 21 */
 588                         return merged_entry(newtree, current);
 589                 }
 590                 else {
 591                         /* all other failures */
 592                         if (oldtree)
 593                                 reject_merge(oldtree);
 594                         if (current)
 595                                 reject_merge(current);
 596                         if (newtree)
 597                                 reject_merge(newtree);
 598                         return -1;
 599                 }
 600         }
 601         else if (newtree)
 602                 return merged_entry(newtree, current);
 603         else
 604                 return deleted_entry(oldtree, current);
 605 }
 606
 607 /*
 608  * One-way merge.
 609  *
 610  * The rule is:
 611  * - take the stat information from stage0, take the data from stage1
 612  */
 613 static int oneway_merge(struct cache_entry **src)
 614 {
 615         struct cache_entry *old = src[0];
 616         struct cache_entry *a = src[1];
 617
 618         if (merge_size != 1)
 619                 return error("Cannot do a oneway merge of %d trees\n",
 620                              merge_size);
 621
 622         if (!a)
 623                 return 0;
 624         if (old && same(old, a)) {
 625                 return keep_entry(old);
 626         }
 627         return merged_entry(a, NULL);
 628 }
 629
 630 static int read_cache_unmerged(void)
 631 {
 632         int i, deleted;
 633         struct cache_entry **dst;
 634
 635         read_cache();
 636         dst = active_cache;
 637         deleted = 0;
 638         for (i = 0; i < active_nr; i++) {
 639                 struct cache_entry *ce = active_cache[i];
 640                 if (ce_stage(ce)) {
 641                         deleted++;
 642                         continue;
 643                 }
 644                 if (deleted)
 645                         *dst = ce;
 646                 dst++;
 647         }
 648         active_nr -= deleted;
 649         return deleted;
 650 }
 651
 652 static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u | -i] <sha1> [<sha2> [<sha3>]])";
 653
 654 static struct cache_file cache_file;
 655
 656 int main(int argc, char **argv)
 657 {
 658         int i, newfd, reset, stage = 0;
 659         unsigned char sha1[20];
 660         merge_fn_t fn = NULL;
 661
 662         setup_git_directory();
 663
 664         newfd = hold_index_file_for_update(&cache_file, get_index_file());
 665         if (newfd < 0)
 666                 die("unable to create new cachefile");
 667
 668         git_config(git_default_config);
 669
 670         merge = 0;
 671         reset = 0;
 672         for (i = 1; i < argc; i++) {
 673                 const char *arg = argv[i];
 674
 675                 /* "-u" means "update", meaning that a merge will update
 676                  * the working tree.
 677                  */
 678                 if (!strcmp(arg, "-u")) {
 679                         update = 1;
 680                         continue;
 681                 }
 682
 683                 /* "-i" means "index only", meaning that a merge will
 684                  * not even look at the working tree.
 685                  */
 686                 if (!strcmp(arg, "-i")) {
 687                         index_only = 1;
 688                         continue;
 689                 }
 690
 691                 /* This differs from "-m" in that we'll silently ignore unmerged entries */
 692                 if (!strcmp(arg, "--reset")) {
 693                         if (stage || merge)
 694                                 usage(read_tree_usage);
 695                         reset = 1;
 696                         merge = 1;
 697                         stage = 1;
 698                         read_cache_unmerged();
 699                         continue;
 700                 }
 701
 702                 if (!strcmp(arg, "--trivial")) {
 703                         trivial_merges_only = 1;
 704                         continue;
 705                 }
 706
 707                 if (!strcmp(arg, "--aggressive")) {
 708                         aggressive = 1;
 709                         continue;
 710                 }
 711
 712                 /* "-m" stands for "merge", meaning we start in stage 1 */
 713                 if (!strcmp(arg, "-m")) {
 714                         if (stage || merge)
 715                                 usage(read_tree_usage);
 716                         if (read_cache_unmerged())
 717                                 die("you need to resolve your current index first");
 718                         stage = 1;
 719                         merge = 1;
 720                         continue;
 721                 }
 722
 723                 /* using -u and -i at the same time makes no sense */
 724                 if (1 < index_only + update)
 725                         usage(read_tree_usage);
 726
 727                 if (get_sha1(arg, sha1) < 0)
 728                         usage(read_tree_usage);
 729                 if (list_tree(sha1) < 0)
 730                         die("failed to unpack tree object %s", arg);
 731                 stage++;
 732         }
 733         if ((update||index_only) && !merge)
 734                 usage(read_tree_usage);
 735
 736         if (merge) {
 737                 if (stage < 2)
 738                         die("just how do you expect me to merge %d trees?", stage-1);
 739                 switch (stage - 1) {
 740                 case 1:
 741                         fn = oneway_merge;
 742                         break;
 743                 case 2:
 744                         fn = twoway_merge;
 745                         break;
 746                 case 3:
 747                         fn = threeway_merge;
 748                         break;
 749                 default:
 750                         fn = threeway_merge;
 751                         break;
 752                 }
 753
 754                 if (stage - 1 >= 3)
 755                         head_idx = stage - 2;
 756                 else
 757                         head_idx = 1;
 758         }
 759
 760         unpack_trees(fn);
 761         if (write_cache(newfd, active_cache, active_nr) ||
 762             commit_index_file(&cache_file))
 763                 die("unable to write new index file");
 764         return 0;
 765 }