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