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