read-tree.c

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