bisect.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "diff.h"
   4 #include "revision.h"
   5 #include "refs.h"
   6 #include "list-objects.h"
   7 #include "quote.h"
   8 #include "sha1-lookup.h"
   9 #include "bisect.h"
  10
  11 static unsigned char (*skipped_sha1)[20];
  12 static int skipped_sha1_nr;
  13 static int skipped_sha1_alloc;
  14
  15 static const char **rev_argv;
  16 static int rev_argv_nr;
  17 static int rev_argv_alloc;
  18
  19 /* bits #0-15 in revision.h */
  20
  21 #define COUNTED         (1u<<16)
  22
  23 /*
  24  * This is a truly stupid algorithm, but it's only
  25  * used for bisection, and we just don't care enough.
  26  *
  27  * We care just barely enough to avoid recursing for
  28  * non-merge entries.
  29  */
  30 static int count_distance(struct commit_list *entry)
  31 {
  32         int nr = 0;
  33
  34         while (entry) {
  35                 struct commit *commit = entry->item;
  36                 struct commit_list *p;
  37
  38                 if (commit->object.flags & (UNINTERESTING | COUNTED))
  39                         break;
  40                 if (!(commit->object.flags & TREESAME))
  41                         nr++;
  42                 commit->object.flags |= COUNTED;
  43                 p = commit->parents;
  44                 entry = p;
  45                 if (p) {
  46                         p = p->next;
  47                         while (p) {
  48                                 nr += count_distance(p);
  49                                 p = p->next;
  50                         }
  51                 }
  52         }
  53
  54         return nr;
  55 }
  56
  57 static void clear_distance(struct commit_list *list)
  58 {
  59         while (list) {
  60                 struct commit *commit = list->item;
  61                 commit->object.flags &= ~COUNTED;
  62                 list = list->next;
  63         }
  64 }
  65
  66 #define DEBUG_BISECT 0
  67
  68 static inline int weight(struct commit_list *elem)
  69 {
  70         return *((int*)(elem->item->util));
  71 }
  72
  73 static inline void weight_set(struct commit_list *elem, int weight)
  74 {
  75         *((int*)(elem->item->util)) = weight;
  76 }
  77
  78 static int count_interesting_parents(struct commit *commit)
  79 {
  80         struct commit_list *p;
  81         int count;
  82
  83         for (count = 0, p = commit->parents; p; p = p->next) {
  84                 if (p->item->object.flags & UNINTERESTING)
  85                         continue;
  86                 count++;
  87         }
  88         return count;
  89 }
  90
  91 static inline int halfway(struct commit_list *p, int nr)
  92 {
  93         /*
  94          * Don't short-cut something we are not going to return!
  95          */
  96         if (p->item->object.flags & TREESAME)
  97                 return 0;
  98         if (DEBUG_BISECT)
  99                 return 0;
 100         /*
 101          * 2 and 3 are halfway of 5.
 102          * 3 is halfway of 6 but 2 and 4 are not.
 103          */
 104         switch (2 * weight(p) - nr) {
 105         case -1: case 0: case 1:
 106                 return 1;
 107         default:
 108                 return 0;
 109         }
 110 }
 111
 112 #if !DEBUG_BISECT
 113 #define show_list(a,b,c,d) do { ; } while (0)
 114 #else
 115 static void show_list(const char *debug, int counted, int nr,
 116                       struct commit_list *list)
 117 {
 118         struct commit_list *p;
 119
 120         fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);
 121
 122         for (p = list; p; p = p->next) {
 123                 struct commit_list *pp;
 124                 struct commit *commit = p->item;
 125                 unsigned flags = commit->object.flags;
 126                 enum object_type type;
 127                 unsigned long size;
 128                 char *buf = read_sha1_file(commit->object.sha1, &type, &size);
 129                 char *ep, *sp;
 130
 131                 fprintf(stderr, "%c%c%c ",
 132                         (flags & TREESAME) ? ' ' : 'T',
 133                         (flags & UNINTERESTING) ? 'U' : ' ',
 134                         (flags & COUNTED) ? 'C' : ' ');
 135                 if (commit->util)
 136                         fprintf(stderr, "%3d", weight(p));
 137                 else
 138                         fprintf(stderr, "---");
 139                 fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.sha1));
 140                 for (pp = commit->parents; pp; pp = pp->next)
 141                         fprintf(stderr, " %.*s", 8,
 142                                 sha1_to_hex(pp->item->object.sha1));
 143
 144                 sp = strstr(buf, "\n\n");
 145                 if (sp) {
 146                         sp += 2;
 147                         for (ep = sp; *ep && *ep != '\n'; ep++)
 148                                 ;
 149                         fprintf(stderr, " %.*s", (int)(ep - sp), sp);
 150                 }
 151                 fprintf(stderr, "\n");
 152         }
 153 }
 154 #endif /* DEBUG_BISECT */
 155
 156 static struct commit_list *best_bisection(struct commit_list *list, int nr)
 157 {
 158         struct commit_list *p, *best;
 159         int best_distance = -1;
 160
 161         best = list;
 162         for (p = list; p; p = p->next) {
 163                 int distance;
 164                 unsigned flags = p->item->object.flags;
 165
 166                 if (flags & TREESAME)
 167                         continue;
 168                 distance = weight(p);
 169                 if (nr - distance < distance)
 170                         distance = nr - distance;
 171                 if (distance > best_distance) {
 172                         best = p;
 173                         best_distance = distance;
 174                 }
 175         }
 176
 177         return best;
 178 }
 179
 180 struct commit_dist {
 181         struct commit *commit;
 182         int distance;
 183 };
 184
 185 static int compare_commit_dist(const void *a_, const void *b_)
 186 {
 187         struct commit_dist *a, *b;
 188
 189         a = (struct commit_dist *)a_;
 190         b = (struct commit_dist *)b_;
 191         if (a->distance != b->distance)
 192                 return b->distance - a->distance; /* desc sort */
 193         return hashcmp(a->commit->object.sha1, b->commit->object.sha1);
 194 }
 195
 196 static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
 197 {
 198         struct commit_list *p;
 199         struct commit_dist *array = xcalloc(nr, sizeof(*array));
 200         int cnt, i;
 201
 202         for (p = list, cnt = 0; p; p = p->next) {
 203                 int distance;
 204                 unsigned flags = p->item->object.flags;
 205
 206                 if (flags & TREESAME)
 207                         continue;
 208                 distance = weight(p);
 209                 if (nr - distance < distance)
 210                         distance = nr - distance;
 211                 array[cnt].commit = p->item;
 212                 array[cnt].distance = distance;
 213                 cnt++;
 214         }
 215         qsort(array, cnt, sizeof(*array), compare_commit_dist);
 216         for (p = list, i = 0; i < cnt; i++) {
 217                 struct name_decoration *r = xmalloc(sizeof(*r) + 100);
 218                 struct object *obj = &(array[i].commit->object);
 219
 220                 sprintf(r->name, "dist=%d", array[i].distance);
 221                 r->next = add_decoration(&name_decoration, obj, r);
 222                 p->item = array[i].commit;
 223                 p = p->next;
 224         }
 225         if (p)
 226                 p->next = NULL;
 227         free(array);
 228         return list;
 229 }
 230
 231 /*
 232  * zero or positive weight is the number of interesting commits it can
 233  * reach, including itself.  Especially, weight = 0 means it does not
 234  * reach any tree-changing commits (e.g. just above uninteresting one
 235  * but traversal is with pathspec).
 236  *
 237  * weight = -1 means it has one parent and its distance is yet to
 238  * be computed.
 239  *
 240  * weight = -2 means it has more than one parent and its distance is
 241  * unknown.  After running count_distance() first, they will get zero
 242  * or positive distance.
 243  */
 244 static struct commit_list *do_find_bisection(struct commit_list *list,
 245                                              int nr, int *weights,
 246                                              int find_all)
 247 {
 248         int n, counted;
 249         struct commit_list *p;
 250
 251         counted = 0;
 252
 253         for (n = 0, p = list; p; p = p->next) {
 254                 struct commit *commit = p->item;
 255                 unsigned flags = commit->object.flags;
 256
 257                 p->item->util = &weights[n++];
 258                 switch (count_interesting_parents(commit)) {
 259                 case 0:
 260                         if (!(flags & TREESAME)) {
 261                                 weight_set(p, 1);
 262                                 counted++;
 263                                 show_list("bisection 2 count one",
 264                                           counted, nr, list);
 265                         }
 266                         /*
 267                          * otherwise, it is known not to reach any
 268                          * tree-changing commit and gets weight 0.
 269                          */
 270                         break;
 271                 case 1:
 272                         weight_set(p, -1);
 273                         break;
 274                 default:
 275                         weight_set(p, -2);
 276                         break;
 277                 }
 278         }
 279
 280         show_list("bisection 2 initialize", counted, nr, list);
 281
 282         /*
 283          * If you have only one parent in the resulting set
 284          * then you can reach one commit more than that parent
 285          * can reach.  So we do not have to run the expensive
 286          * count_distance() for single strand of pearls.
 287          *
 288          * However, if you have more than one parents, you cannot
 289          * just add their distance and one for yourself, since
 290          * they usually reach the same ancestor and you would
 291          * end up counting them twice that way.
 292          *
 293          * So we will first count distance of merges the usual
 294          * way, and then fill the blanks using cheaper algorithm.
 295          */
 296         for (p = list; p; p = p->next) {
 297                 if (p->item->object.flags & UNINTERESTING)
 298                         continue;
 299                 if (weight(p) != -2)
 300                         continue;
 301                 weight_set(p, count_distance(p));
 302                 clear_distance(list);
 303
 304                 /* Does it happen to be at exactly half-way? */
 305                 if (!find_all && halfway(p, nr))
 306                         return p;
 307                 counted++;
 308         }
 309
 310         show_list("bisection 2 count_distance", counted, nr, list);
 311
 312         while (counted < nr) {
 313                 for (p = list; p; p = p->next) {
 314                         struct commit_list *q;
 315                         unsigned flags = p->item->object.flags;
 316
 317                         if (0 <= weight(p))
 318                                 continue;
 319                         for (q = p->item->parents; q; q = q->next) {
 320                                 if (q->item->object.flags & UNINTERESTING)
 321                                         continue;
 322                                 if (0 <= weight(q))
 323                                         break;
 324                         }
 325                         if (!q)
 326                                 continue;
 327
 328                         /*
 329                          * weight for p is unknown but q is known.
 330                          * add one for p itself if p is to be counted,
 331                          * otherwise inherit it from q directly.
 332                          */
 333                         if (!(flags & TREESAME)) {
 334                                 weight_set(p, weight(q)+1);
 335                                 counted++;
 336                                 show_list("bisection 2 count one",
 337                                           counted, nr, list);
 338                         }
 339                         else
 340                                 weight_set(p, weight(q));
 341
 342                         /* Does it happen to be at exactly half-way? */
 343                         if (!find_all && halfway(p, nr))
 344                                 return p;
 345                 }
 346         }
 347
 348         show_list("bisection 2 counted all", counted, nr, list);
 349
 350         if (!find_all)
 351                 return best_bisection(list, nr);
 352         else
 353                 return best_bisection_sorted(list, nr);
 354 }
 355
 356 struct commit_list *find_bisection(struct commit_list *list,
 357                                           int *reaches, int *all,
 358                                           int find_all)
 359 {
 360         int nr, on_list;
 361         struct commit_list *p, *best, *next, *last;
 362         int *weights;
 363
 364         show_list("bisection 2 entry", 0, 0, list);
 365
 366         /*
 367          * Count the number of total and tree-changing items on the
 368          * list, while reversing the list.
 369          */
 370         for (nr = on_list = 0, last = NULL, p = list;
 371              p;
 372              p = next) {
 373                 unsigned flags = p->item->object.flags;
 374
 375                 next = p->next;
 376                 if (flags & UNINTERESTING)
 377                         continue;
 378                 p->next = last;
 379                 last = p;
 380                 if (!(flags & TREESAME))
 381                         nr++;
 382                 on_list++;
 383         }
 384         list = last;
 385         show_list("bisection 2 sorted", 0, nr, list);
 386
 387         *all = nr;
 388         weights = xcalloc(on_list, sizeof(*weights));
 389
 390         /* Do the real work of finding bisection commit. */
 391         best = do_find_bisection(list, nr, weights, find_all);
 392         if (best) {
 393                 if (!find_all)
 394                         best->next = NULL;
 395                 *reaches = weight(best);
 396         }
 397         free(weights);
 398         return best;
 399 }
 400
 401 static int register_ref(const char *refname, const unsigned char *sha1,
 402                         int flags, void *cb_data)
 403 {
 404         if (!strcmp(refname, "bad")) {
 405                 ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
 406                 rev_argv[rev_argv_nr++] = xstrdup(sha1_to_hex(sha1));
 407         } else if (!prefixcmp(refname, "good-")) {
 408                 const char *hex = sha1_to_hex(sha1);
 409                 char *good = xmalloc(strlen(hex) + 2);
 410                 *good = '^';
 411                 memcpy(good + 1, hex, strlen(hex) + 1);
 412                 ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
 413                 rev_argv[rev_argv_nr++] = good;
 414         } else if (!prefixcmp(refname, "skip-")) {
 415                 ALLOC_GROW(skipped_sha1, skipped_sha1_nr + 1,
 416                            skipped_sha1_alloc);
 417                 hashcpy(skipped_sha1[skipped_sha1_nr++], sha1);
 418         }
 419
 420         return 0;
 421 }
 422
 423 static int read_bisect_refs(void)
 424 {
 425         return for_each_ref_in("refs/bisect/", register_ref, NULL);
 426 }
 427
 428 void read_bisect_paths(void)
 429 {
 430         struct strbuf str = STRBUF_INIT;
 431         const char *filename = git_path("BISECT_NAMES");
 432         FILE *fp = fopen(filename, "r");
 433
 434         if (!fp)
 435                 die("Could not open file '%s': %s", filename, strerror(errno));
 436
 437         while (strbuf_getline(&str, fp, '\n') != EOF) {
 438                 char *quoted;
 439                 int res;
 440
 441                 strbuf_trim(&str);
 442                 quoted = strbuf_detach(&str, NULL);
 443                 res = sq_dequote_to_argv(quoted, &rev_argv,
 444                                          &rev_argv_nr, &rev_argv_alloc);
 445                 if (res)
 446                         die("Badly quoted content in file '%s': %s",
 447                             filename, quoted);
 448         }
 449
 450         strbuf_release(&str);
 451         fclose(fp);
 452 }
 453
 454 static int skipcmp(const void *a, const void *b)
 455 {
 456         return hashcmp(a, b);
 457 }
 458
 459 static void prepare_skipped(void)
 460 {
 461         qsort(skipped_sha1, skipped_sha1_nr, sizeof(*skipped_sha1), skipcmp);
 462 }
 463
 464 static const unsigned char *skipped_sha1_access(size_t index, void *table)
 465 {
 466         unsigned char (*skipped)[20] = table;
 467         return skipped[index];
 468 }
 469
 470 static int lookup_skipped(unsigned char *sha1)
 471 {
 472         return sha1_pos(sha1, skipped_sha1, skipped_sha1_nr,
 473                         skipped_sha1_access);
 474 }
 475
 476 struct commit_list *filter_skipped(struct commit_list *list,
 477                                    struct commit_list **tried,
 478                                    int show_all)
 479 {
 480         struct commit_list *filtered = NULL, **f = &filtered;
 481
 482         *tried = NULL;
 483
 484         if (!skipped_sha1_nr)
 485                 return list;
 486
 487         prepare_skipped();
 488
 489         while (list) {
 490                 struct commit_list *next = list->next;
 491                 list->next = NULL;
 492                 if (0 <= lookup_skipped(list->item->object.sha1)) {
 493                         /* Move current to tried list */
 494                         *tried = list;
 495                         tried = &list->next;
 496                 } else {
 497                         if (!show_all)
 498                                 return list;
 499                         /* Move current to filtered list */
 500                         *f = list;
 501                         f = &list->next;
 502                 }
 503                 list = next;
 504         }
 505
 506         return filtered;
 507 }
 508
 509 static void bisect_rev_setup(struct rev_info *revs, const char *prefix)
 510 {
 511         init_revisions(revs, prefix);
 512         revs->abbrev = 0;
 513         revs->commit_format = CMIT_FMT_UNSPECIFIED;
 514
 515         /* argv[0] will be ignored by setup_revisions */
 516         ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
 517         rev_argv[rev_argv_nr++] = xstrdup("bisect_rev_setup");
 518
 519         if (read_bisect_refs())
 520                 die("reading bisect refs failed");
 521
 522         ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
 523         rev_argv[rev_argv_nr++] = xstrdup("--");
 524
 525         read_bisect_paths();
 526
 527         ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
 528         rev_argv[rev_argv_nr++] = NULL;
 529
 530         setup_revisions(rev_argv_nr, rev_argv, revs, NULL);
 531
 532         revs->limited = 1;
 533 }
 534
 535 int bisect_next_vars(const char *prefix)
 536 {
 537         struct rev_info revs;
 538         int reaches = 0, all = 0;
 539
 540         bisect_rev_setup(&revs, prefix);
 541
 542         if (prepare_revision_walk(&revs))
 543                 die("revision walk setup failed");
 544         if (revs.tree_objects)
 545                 mark_edges_uninteresting(revs.commits, &revs, NULL);
 546
 547         revs.commits = find_bisection(revs.commits, &reaches, &all,
 548                                       !!skipped_sha1_nr);
 549
 550         return show_bisect_vars(&revs, reaches, all, 0, 1);
 551 }