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
  16 static int head_idx = -1;
  17 static int merge_size = 0;
  18
  19 static struct object_list *trees = NULL;
  20
  21 static struct cache_entry df_conflict_entry = {
  22 };
  23
  24 static struct tree_entry_list df_conflict_list = {
  25         .name = NULL,
  26         .next = &df_conflict_list
  27 };
  28
  29 typedef int (*merge_fn_t)(struct cache_entry **src);
  30
  31 static int entcmp(char *name1, int dir1, char *name2, int dir2)
  32 {
  33         int len1 = strlen(name1);
  34         int len2 = strlen(name2);
  35         int len = len1 < len2 ? len1 : len2;
  36         int ret = memcmp(name1, name2, len);
  37         unsigned char c1, c2;
  38         if (ret)
  39                 return ret;
  40         c1 = name1[len];
  41         c2 = name2[len];
  42         if (!c1 && dir1)
  43                 c1 = '/';
  44         if (!c2 && dir2)
  45                 c2 = '/';
  46         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  47         if (c1 && c2 && !ret)
  48                 ret = len1 - len2;
  49         return ret;
  50 }
  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 > 1
 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 > 1
 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 > 1
 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 > 1
 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 #if DBRT_DEBUG
 357 static void show_stage_entry(FILE *o,
 358                              const char *label, const struct cache_entry *ce)
 359 {
 360         fprintf(stderr, "%s%06o %s %d\t%s\n",
 361                 label,
 362                 ntohl(ce->ce_mode),
 363                 sha1_to_hex(ce->sha1),
 364                 ce_stage(ce),
 365                 ce->name);
 366 }
 367 #endif
 368
 369 static int threeway_merge(struct cache_entry **stages)
 370 {
 371         struct cache_entry *index;
 372         struct cache_entry *head;
 373         struct cache_entry *remote = stages[head_idx + 1];
 374         int count;
 375         int head_match = 0;
 376         int remote_match = 0;
 377
 378         int df_conflict_head = 0;
 379         int df_conflict_remote = 0;
 380
 381         int any_anc_missing = 0;
 382         int i;
 383
 384         for (i = 1; i < head_idx; i++) {
 385                 if (!stages[i])
 386                         any_anc_missing = 1;
 387         }
 388
 389         index = stages[0];
 390         head = stages[head_idx];
 391
 392         if (head == &df_conflict_entry) {
 393                 df_conflict_head = 1;
 394                 head = NULL;
 395         }
 396
 397         if (remote == &df_conflict_entry) {
 398                 df_conflict_remote = 1;
 399                 remote = NULL;
 400         }
 401
 402         /* First, if there's a #16 situation, note that to prevent #13
 403          * and #14.
 404          */
 405         if (!same(remote, head)) {
 406                 for (i = 1; i < head_idx; i++) {
 407                         if (same(stages[i], head)) {
 408                                 head_match = i;
 409                         }
 410                         if (same(stages[i], remote)) {
 411                                 remote_match = i;
 412                         }
 413                 }
 414         }
 415
 416         /* We start with cases where the index is allowed to match
 417          * something other than the head: #14(ALT) and #2ALT, where it
 418          * is permitted to match the result instead.
 419          */
 420         /* #14, #14ALT, #2ALT */
 421         if (remote && !df_conflict_head && head_match && !remote_match) {
 422                 if (index && !same(index, remote) && !same(index, head))
 423                         reject_merge(index);
 424                 return merged_entry(remote, index);
 425         }
 426         /*
 427          * If we have an entry in the index cache, then we want to
 428          * make sure that it matches head.
 429          */
 430         if (index && !same(index, head)) {
 431                 reject_merge(index);
 432         }
 433
 434         if (head) {
 435                 /* #5ALT, #15 */
 436                 if (same(head, remote))
 437                         return merged_entry(head, index);
 438                 /* #13, #3ALT */
 439                 if (!df_conflict_remote && remote_match && !head_match)
 440                         return merged_entry(head, index);
 441         }
 442
 443         /* #1 */
 444         if (!head && !remote && any_anc_missing)
 445                 return 0;
 446
 447         /* Below are "no merge" cases, which require that the index be
 448          * up-to-date to avoid the files getting overwritten with
 449          * conflict resolution files.
 450          */
 451         if (index) {
 452                 verify_uptodate(index);
 453         }
 454
 455         /* #2, #3, #4, #6, #7, #9, #11. */
 456         count = 0;
 457         if (!head_match || !remote_match) {
 458                 for (i = 1; i < head_idx; i++) {
 459                         if (stages[i]) {
 460                                 keep_entry(stages[i]);
 461                                 count++;
 462                                 break;
 463                         }
 464                 }
 465         }
 466 #if DBRT_DEBUG
 467         else {
 468                 fprintf(stderr, "read-tree: warning #16 detected\n");
 469                 show_stage_entry(stderr, "head   ", stages[head_match]);
 470                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 471         }
 472 #endif
 473         if (head) { count += keep_entry(head); }
 474         if (remote) { count += keep_entry(remote); }
 475         return count;
 476 }
 477
 478 /*
 479  * Two-way merge.
 480  *
 481  * The rule is to "carry forward" what is in the index without losing
 482  * information across a "fast forward", favoring a successful merge
 483  * over a merge failure when it makes sense.  For details of the
 484  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 485  *
 486  */
 487 static int twoway_merge(struct cache_entry **src)
 488 {
 489         struct cache_entry *current = src[0];
 490         struct cache_entry *oldtree = src[1], *newtree = src[2];
 491
 492         if (merge_size != 2)
 493                 return error("Cannot do a twoway merge of %d trees\n",
 494                              merge_size);
 495
 496         if (current) {
 497                 if ((!oldtree && !newtree) || /* 4 and 5 */
 498                     (!oldtree && newtree &&
 499                      same(current, newtree)) || /* 6 and 7 */
 500                     (oldtree && newtree &&
 501                      same(oldtree, newtree)) || /* 14 and 15 */
 502                     (oldtree && newtree &&
 503                      !same(oldtree, newtree) && /* 18 and 19*/
 504                      same(current, newtree))) {
 505                         return keep_entry(current);
 506                 }
 507                 else if (oldtree && !newtree && same(current, oldtree)) {
 508                         /* 10 or 11 */
 509                         return deleted_entry(oldtree, current);
 510                 }
 511                 else if (oldtree && newtree &&
 512                          same(current, oldtree) && !same(current, newtree)) {
 513                         /* 20 or 21 */
 514                         return merged_entry(newtree, current);
 515                 }
 516                 else {
 517                         /* all other failures */
 518                         if (oldtree)
 519                                 reject_merge(oldtree);
 520                         if (current)
 521                                 reject_merge(current);
 522                         if (newtree)
 523                                 reject_merge(newtree);
 524                         return -1;
 525                 }
 526         }
 527         else if (newtree)
 528                 return merged_entry(newtree, current);
 529         else
 530                 return deleted_entry(oldtree, current);
 531 }
 532
 533 /*
 534  * One-way merge.
 535  *
 536  * The rule is:
 537  * - take the stat information from stage0, take the data from stage1
 538  */
 539 static int oneway_merge(struct cache_entry **src)
 540 {
 541         struct cache_entry *old = src[0];
 542         struct cache_entry *a = src[1];
 543
 544         if (merge_size != 1)
 545                 return error("Cannot do a oneway merge of %d trees\n",
 546                              merge_size);
 547
 548         if (!a)
 549                 return 0;
 550         if (old && same(old, a)) {
 551                 return keep_entry(old);
 552         }
 553         return merged_entry(a, NULL);
 554 }
 555
 556 static int read_cache_unmerged(void)
 557 {
 558         int i, deleted;
 559         struct cache_entry **dst;
 560
 561         read_cache();
 562         dst = active_cache;
 563         deleted = 0;
 564         for (i = 0; i < active_nr; i++) {
 565                 struct cache_entry *ce = active_cache[i];
 566                 if (ce_stage(ce)) {
 567                         deleted++;
 568                         continue;
 569                 }
 570                 if (deleted)
 571                         *dst = ce;
 572                 dst++;
 573         }
 574         active_nr -= deleted;
 575         return deleted;
 576 }
 577
 578 static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u] <sha1> [<sha2> [<sha3>]])";
 579
 580 static struct cache_file cache_file;
 581
 582 int main(int argc, char **argv)
 583 {
 584         int i, newfd, reset, stage = 0;
 585         unsigned char sha1[20];
 586         merge_fn_t fn = NULL;
 587
 588         newfd = hold_index_file_for_update(&cache_file, get_index_file());
 589         if (newfd < 0)
 590                 die("unable to create new cachefile");
 591
 592         merge = 0;
 593         reset = 0;
 594         for (i = 1; i < argc; i++) {
 595                 const char *arg = argv[i];
 596
 597                 /* "-u" means "update", meaning that a merge will update the working directory */
 598                 if (!strcmp(arg, "-u")) {
 599                         update = 1;
 600                         continue;
 601                 }
 602
 603                 /* This differs from "-m" in that we'll silently ignore unmerged entries */
 604                 if (!strcmp(arg, "--reset")) {
 605                         if (stage || merge)
 606                                 usage(read_tree_usage);
 607                         reset = 1;
 608                         merge = 1;
 609                         stage = 1;
 610                         read_cache_unmerged();
 611                         continue;
 612                 }
 613
 614                 if (!strcmp(arg, "--head")) {
 615                         head_idx = stage - 1;
 616                         fn = threeway_merge;
 617                 }
 618
 619                 /* "-m" stands for "merge", meaning we start in stage 1 */
 620                 if (!strcmp(arg, "-m")) {
 621                         if (stage || merge)
 622                                 usage(read_tree_usage);
 623                         if (read_cache_unmerged())
 624                                 die("you need to resolve your current index first");
 625                         stage = 1;
 626                         merge = 1;
 627                         continue;
 628                 }
 629
 630                 if (get_sha1(arg, sha1) < 0)
 631                         usage(read_tree_usage);
 632                 if (list_tree(sha1) < 0)
 633                         die("failed to unpack tree object %s", arg);
 634                 stage++;
 635         }
 636         if (update && !merge)
 637                 usage(read_tree_usage);
 638         if (merge && !fn) {
 639                 if (stage < 2)
 640                         die("just how do you expect me to merge %d trees?", stage-1);
 641                 switch (stage - 1) {
 642                 case 1:
 643                         fn = oneway_merge;
 644                         break;
 645                 case 2:
 646                         fn = twoway_merge;
 647                         break;
 648                 case 3:
 649                         fn = threeway_merge;
 650                         break;
 651                 default:
 652                         fn = threeway_merge;
 653                         break;
 654                 }
 655         }
 656
 657         if (head_idx < 0) {
 658                 if (stage - 1 >= 3)
 659                         head_idx = stage - 2;
 660                 else
 661                         head_idx = 1;
 662         }
 663
 664         unpack_trees(fn);
 665         if (write_cache(newfd, active_cache, active_nr) ||
 666             commit_index_file(&cache_file))
 667                 die("unable to write new index file");
 668         return 0;
 669 }