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                         free(newbase);
 225                 }
 226                 free(subposns);
 227                 free(src);
 228         } while (1);
 229 }
 230
 231 static void reject_merge(struct cache_entry *ce)
 232 {
 233         die("Entry '%s' would be overwritten by merge. Cannot merge.",
 234             ce->name);
 235 }
 236
 237 static void check_updates(struct cache_entry **src, int nr)
 238 {
 239         static struct checkout state = {
 240                 .base_dir = "",
 241                 .force = 1,
 242                 .quiet = 1,
 243                 .refresh_cache = 1,
 244         };
 245         unsigned short mask = htons(CE_UPDATE);
 246         while (nr--) {
 247                 struct cache_entry *ce = *src++;
 248                 if (!ce->ce_mode) {
 249                         if (update)
 250                                 unlink(ce->name);
 251                         continue;
 252                 }
 253                 if (ce->ce_flags & mask) {
 254                         ce->ce_flags &= ~mask;
 255                         if (update)
 256                                 checkout_entry(ce, &state);
 257                 }
 258         }
 259 }
 260
 261 static int unpack_trees(merge_fn_t fn)
 262 {
 263         int indpos = 0;
 264         unsigned len = object_list_length(trees);
 265         struct tree_entry_list **posns =
 266                 xmalloc(len * sizeof(struct tree_entry_list *));
 267         int i;
 268         struct object_list *posn = trees;
 269         merge_size = len;
 270         for (i = 0; i < len; i++) {
 271                 posns[i] = ((struct tree *) posn->item)->entries;
 272                 posn = posn->next;
 273         }
 274         if (unpack_trees_rec(posns, len, "", fn, &indpos))
 275                 return -1;
 276
 277         check_updates(active_cache, active_nr);
 278         return 0;
 279 }
 280
 281 static int list_tree(unsigned char *sha1)
 282 {
 283         struct tree *tree = parse_tree_indirect(sha1);
 284         if (!tree)
 285                 return -1;
 286         object_list_append(&tree->object, &trees);
 287         return 0;
 288 }
 289
 290 static int same(struct cache_entry *a, struct cache_entry *b)
 291 {
 292         if (!!a != !!b)
 293                 return 0;
 294         if (!a && !b)
 295                 return 1;
 296         return a->ce_mode == b->ce_mode &&
 297                 !memcmp(a->sha1, b->sha1, 20);
 298 }
 299
 300
 301 /*
 302  * When a CE gets turned into an unmerged entry, we
 303  * want it to be up-to-date
 304  */
 305 static void verify_uptodate(struct cache_entry *ce)
 306 {
 307         struct stat st;
 308
 309         if (!lstat(ce->name, &st)) {
 310                 unsigned changed = ce_match_stat(ce, &st);
 311                 if (!changed)
 312                         return;
 313                 errno = 0;
 314         }
 315         if (errno == ENOENT)
 316                 return;
 317         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 318 }
 319
 320 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 321 {
 322         merge->ce_flags |= htons(CE_UPDATE);
 323         if (old) {
 324                 /*
 325                  * See if we can re-use the old CE directly?
 326                  * That way we get the uptodate stat info.
 327                  *
 328                  * This also removes the UPDATE flag on
 329                  * a match.
 330                  */
 331                 if (same(old, merge)) {
 332                         *merge = *old;
 333                 } else {
 334                         verify_uptodate(old);
 335                 }
 336         }
 337         merge->ce_flags &= ~htons(CE_STAGEMASK);
 338         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 339         return 1;
 340 }
 341
 342 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 343 {
 344         if (old)
 345                 verify_uptodate(old);
 346         ce->ce_mode = 0;
 347         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 348         return 1;
 349 }
 350
 351 static int keep_entry(struct cache_entry *ce)
 352 {
 353         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 354         return 1;
 355 }
 356
 357 #if DBRT_DEBUG
 358 static void show_stage_entry(FILE *o,
 359                              const char *label, const struct cache_entry *ce)
 360 {
 361         fprintf(stderr, "%s%06o %s %d\t%s\n",
 362                 label,
 363                 ntohl(ce->ce_mode),
 364                 sha1_to_hex(ce->sha1),
 365                 ce_stage(ce),
 366                 ce->name);
 367 }
 368 #endif
 369
 370 static int threeway_merge(struct cache_entry **stages)
 371 {
 372         struct cache_entry *index;
 373         struct cache_entry *head;
 374         struct cache_entry *remote = stages[head_idx + 1];
 375         int count;
 376         int head_match = 0;
 377         int remote_match = 0;
 378
 379         int df_conflict_head = 0;
 380         int df_conflict_remote = 0;
 381
 382         int any_anc_missing = 0;
 383         int i;
 384
 385         for (i = 1; i < head_idx; i++) {
 386                 if (!stages[i])
 387                         any_anc_missing = 1;
 388         }
 389
 390         index = stages[0];
 391         head = stages[head_idx];
 392
 393         if (head == &df_conflict_entry) {
 394                 df_conflict_head = 1;
 395                 head = NULL;
 396         }
 397
 398         if (remote == &df_conflict_entry) {
 399                 df_conflict_remote = 1;
 400                 remote = NULL;
 401         }
 402
 403         /* First, if there's a #16 situation, note that to prevent #13
 404          * and #14.
 405          */
 406         if (!same(remote, head)) {
 407                 for (i = 1; i < head_idx; i++) {
 408                         if (same(stages[i], head)) {
 409                                 head_match = i;
 410                         }
 411                         if (same(stages[i], remote)) {
 412                                 remote_match = i;
 413                         }
 414                 }
 415         }
 416
 417         /* We start with cases where the index is allowed to match
 418          * something other than the head: #14(ALT) and #2ALT, where it
 419          * is permitted to match the result instead.
 420          */
 421         /* #14, #14ALT, #2ALT */
 422         if (remote && !df_conflict_head && head_match && !remote_match) {
 423                 if (index && !same(index, remote) && !same(index, head))
 424                         reject_merge(index);
 425                 return merged_entry(remote, index);
 426         }
 427         /*
 428          * If we have an entry in the index cache, then we want to
 429          * make sure that it matches head.
 430          */
 431         if (index && !same(index, head)) {
 432                 reject_merge(index);
 433         }
 434
 435         if (head) {
 436                 /* #5ALT, #15 */
 437                 if (same(head, remote))
 438                         return merged_entry(head, index);
 439                 /* #13, #3ALT */
 440                 if (!df_conflict_remote && remote_match && !head_match)
 441                         return merged_entry(head, index);
 442         }
 443
 444         /* #1 */
 445         if (!head && !remote && any_anc_missing)
 446                 return 0;
 447
 448         /* Below are "no merge" cases, which require that the index be
 449          * up-to-date to avoid the files getting overwritten with
 450          * conflict resolution files.
 451          */
 452         if (index) {
 453                 verify_uptodate(index);
 454         }
 455
 456         /* #2, #3, #4, #6, #7, #9, #11. */
 457         count = 0;
 458         if (!head_match || !remote_match) {
 459                 for (i = 1; i < head_idx; i++) {
 460                         if (stages[i]) {
 461                                 keep_entry(stages[i]);
 462                                 count++;
 463                                 break;
 464                         }
 465                 }
 466         }
 467 #if DBRT_DEBUG
 468         else {
 469                 fprintf(stderr, "read-tree: warning #16 detected\n");
 470                 show_stage_entry(stderr, "head   ", stages[head_match]);
 471                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 472         }
 473 #endif
 474         if (head) { count += keep_entry(head); }
 475         if (remote) { count += keep_entry(remote); }
 476         return count;
 477 }
 478
 479 /*
 480  * Two-way merge.
 481  *
 482  * The rule is to "carry forward" what is in the index without losing
 483  * information across a "fast forward", favoring a successful merge
 484  * over a merge failure when it makes sense.  For details of the
 485  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 486  *
 487  */
 488 static int twoway_merge(struct cache_entry **src)
 489 {
 490         struct cache_entry *current = src[0];
 491         struct cache_entry *oldtree = src[1], *newtree = src[2];
 492
 493         if (merge_size != 2)
 494                 return error("Cannot do a twoway merge of %d trees\n",
 495                              merge_size);
 496
 497         if (current) {
 498                 if ((!oldtree && !newtree) || /* 4 and 5 */
 499                     (!oldtree && newtree &&
 500                      same(current, newtree)) || /* 6 and 7 */
 501                     (oldtree && newtree &&
 502                      same(oldtree, newtree)) || /* 14 and 15 */
 503                     (oldtree && newtree &&
 504                      !same(oldtree, newtree) && /* 18 and 19*/
 505                      same(current, newtree))) {
 506                         return keep_entry(current);
 507                 }
 508                 else if (oldtree && !newtree && same(current, oldtree)) {
 509                         /* 10 or 11 */
 510                         return deleted_entry(oldtree, current);
 511                 }
 512                 else if (oldtree && newtree &&
 513                          same(current, oldtree) && !same(current, newtree)) {
 514                         /* 20 or 21 */
 515                         return merged_entry(newtree, current);
 516                 }
 517                 else {
 518                         /* all other failures */
 519                         if (oldtree)
 520                                 reject_merge(oldtree);
 521                         if (current)
 522                                 reject_merge(current);
 523                         if (newtree)
 524                                 reject_merge(newtree);
 525                         return -1;
 526                 }
 527         }
 528         else if (newtree)
 529                 return merged_entry(newtree, current);
 530         else
 531                 return deleted_entry(oldtree, current);
 532 }
 533
 534 /*
 535  * One-way merge.
 536  *
 537  * The rule is:
 538  * - take the stat information from stage0, take the data from stage1
 539  */
 540 static int oneway_merge(struct cache_entry **src)
 541 {
 542         struct cache_entry *old = src[0];
 543         struct cache_entry *a = src[1];
 544
 545         if (merge_size != 1)
 546                 return error("Cannot do a oneway merge of %d trees\n",
 547                              merge_size);
 548
 549         if (!a)
 550                 return 0;
 551         if (old && same(old, a)) {
 552                 return keep_entry(old);
 553         }
 554         return merged_entry(a, NULL);
 555 }
 556
 557 static int read_cache_unmerged(void)
 558 {
 559         int i, deleted;
 560         struct cache_entry **dst;
 561
 562         read_cache();
 563         dst = active_cache;
 564         deleted = 0;
 565         for (i = 0; i < active_nr; i++) {
 566                 struct cache_entry *ce = active_cache[i];
 567                 if (ce_stage(ce)) {
 568                         deleted++;
 569                         continue;
 570                 }
 571                 if (deleted)
 572                         *dst = ce;
 573                 dst++;
 574         }
 575         active_nr -= deleted;
 576         return deleted;
 577 }
 578
 579 static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u] <sha1> [<sha2> [<sha3>]])";
 580
 581 static struct cache_file cache_file;
 582
 583 int main(int argc, char **argv)
 584 {
 585         int i, newfd, reset, stage = 0;
 586         unsigned char sha1[20];
 587         merge_fn_t fn = NULL;
 588
 589         newfd = hold_index_file_for_update(&cache_file, get_index_file());
 590         if (newfd < 0)
 591                 die("unable to create new cachefile");
 592
 593         merge = 0;
 594         reset = 0;
 595         for (i = 1; i < argc; i++) {
 596                 const char *arg = argv[i];
 597
 598                 /* "-u" means "update", meaning that a merge will update the working directory */
 599                 if (!strcmp(arg, "-u")) {
 600                         update = 1;
 601                         continue;
 602                 }
 603
 604                 /* This differs from "-m" in that we'll silently ignore unmerged entries */
 605                 if (!strcmp(arg, "--reset")) {
 606                         if (stage || merge)
 607                                 usage(read_tree_usage);
 608                         reset = 1;
 609                         merge = 1;
 610                         stage = 1;
 611                         read_cache_unmerged();
 612                         continue;
 613                 }
 614
 615                 if (!strcmp(arg, "--head")) {
 616                         head_idx = stage - 1;
 617                         fn = threeway_merge;
 618                 }
 619
 620                 /* "-m" stands for "merge", meaning we start in stage 1 */
 621                 if (!strcmp(arg, "-m")) {
 622                         if (stage || merge)
 623                                 usage(read_tree_usage);
 624                         if (read_cache_unmerged())
 625                                 die("you need to resolve your current index first");
 626                         stage = 1;
 627                         merge = 1;
 628                         continue;
 629                 }
 630
 631                 if (get_sha1(arg, sha1) < 0)
 632                         usage(read_tree_usage);
 633                 if (list_tree(sha1) < 0)
 634                         die("failed to unpack tree object %s", arg);
 635                 stage++;
 636         }
 637         if (update && !merge)
 638                 usage(read_tree_usage);
 639         if (merge && !fn) {
 640                 if (stage < 2)
 641                         die("just how do you expect me to merge %d trees?", stage-1);
 642                 switch (stage - 1) {
 643                 case 1:
 644                         fn = oneway_merge;
 645                         break;
 646                 case 2:
 647                         fn = twoway_merge;
 648                         break;
 649                 case 3:
 650                         fn = threeway_merge;
 651                         break;
 652                 default:
 653                         fn = threeway_merge;
 654                         break;
 655                 }
 656         }
 657
 658         if (head_idx < 0) {
 659                 if (stage - 1 >= 3)
 660                         head_idx = stage - 2;
 661                 else
 662                         head_idx = 1;
 663         }
 664
 665         unpack_trees(fn);
 666         if (write_cache(newfd, active_cache, active_nr) ||
 667             commit_index_file(&cache_file))
 668                 die("unable to write new index file");
 669         return 0;
 670 }