git.oblomov.eu Git - git/blob - shallow.c

   1 #include "cache.h"
   2 #include "tempfile.h"
   3 #include "lockfile.h"
   4 #include "commit.h"
   5 #include "tag.h"
   6 #include "pkt-line.h"
   7 #include "remote.h"
   8 #include "refs.h"
   9 #include "sha1-array.h"
  10 #include "diff.h"
  11 #include "revision.h"
  12 #include "commit-slab.h"
  13
  14 static int is_shallow = -1;
  15 static struct stat_validity shallow_stat;
  16 static char *alternate_shallow_file;
  17
  18 void set_alternate_shallow_file(const char *path, int override)
  19 {
  20         if (is_shallow != -1)
  21                 die("BUG: is_repository_shallow must not be called before set_alternate_shallow_file");
  22         if (alternate_shallow_file && !override)
  23                 return;
  24         free(alternate_shallow_file);
  25         alternate_shallow_file = xstrdup_or_null(path);
  26 }
  27
  28 int register_shallow(const unsigned char *sha1)
  29 {
  30         struct commit_graft *graft =
  31                 xmalloc(sizeof(struct commit_graft));
  32         struct commit *commit = lookup_commit(sha1);
  33
  34         hashcpy(graft->oid.hash, sha1);
  35         graft->nr_parent = -1;
  36         if (commit && commit->object.parsed)
  37                 commit->parents = NULL;
  38         return register_commit_graft(graft, 0);
  39 }
  40
  41 int is_repository_shallow(void)
  42 {
  43         FILE *fp;
  44         char buf[1024];
  45         const char *path = alternate_shallow_file;
  46
  47         if (is_shallow >= 0)
  48                 return is_shallow;
  49
  50         if (!path)
  51                 path = git_path_shallow();
  52         /*
  53          * fetch-pack sets '--shallow-file ""' as an indicator that no
  54          * shallow file should be used. We could just open it and it
  55          * will likely fail. But let's do an explicit check instead.
  56          */
  57         if (!*path || (fp = fopen(path, "r")) == NULL) {
  58                 stat_validity_clear(&shallow_stat);
  59                 is_shallow = 0;
  60                 return is_shallow;
  61         }
  62         stat_validity_update(&shallow_stat, fileno(fp));
  63         is_shallow = 1;
  64
  65         while (fgets(buf, sizeof(buf), fp)) {
  66                 unsigned char sha1[20];
  67                 if (get_sha1_hex(buf, sha1))
  68                         die("bad shallow line: %s", buf);
  69                 register_shallow(sha1);
  70         }
  71         fclose(fp);
  72         return is_shallow;
  73 }
  74
  75 struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
  76                 int shallow_flag, int not_shallow_flag)
  77 {
  78         int i = 0, cur_depth = 0;
  79         struct commit_list *result = NULL;
  80         struct object_array stack = OBJECT_ARRAY_INIT;
  81         struct commit *commit = NULL;
  82         struct commit_graft *graft;
  83
  84         while (commit || i < heads->nr || stack.nr) {
  85                 struct commit_list *p;
  86                 if (!commit) {
  87                         if (i < heads->nr) {
  88                                 commit = (struct commit *)
  89                                         deref_tag(heads->objects[i++].item, NULL, 0);
  90                                 if (!commit || commit->object.type != OBJ_COMMIT) {
  91                                         commit = NULL;
  92                                         continue;
  93                                 }
  94                                 if (!commit->util)
  95                                         commit->util = xmalloc(sizeof(int));
  96                                 *(int *)commit->util = 0;
  97                                 cur_depth = 0;
  98                         } else {
  99                                 commit = (struct commit *)
 100                                         stack.objects[--stack.nr].item;
 101                                 cur_depth = *(int *)commit->util;
 102                         }
 103                 }
 104                 parse_commit_or_die(commit);
 105                 cur_depth++;
 106                 if ((depth != INFINITE_DEPTH && cur_depth >= depth) ||
 107                     (is_repository_shallow() && !commit->parents &&
 108                      (graft = lookup_commit_graft(commit->object.sha1)) != NULL &&
 109                      graft->nr_parent < 0)) {
 110                         commit_list_insert(commit, &result);
 111                         commit->object.flags |= shallow_flag;
 112                         commit = NULL;
 113                         continue;
 114                 }
 115                 commit->object.flags |= not_shallow_flag;
 116                 for (p = commit->parents, commit = NULL; p; p = p->next) {
 117                         if (!p->item->util) {
 118                                 int *pointer = xmalloc(sizeof(int));
 119                                 p->item->util = pointer;
 120                                 *pointer =  cur_depth;
 121                         } else {
 122                                 int *pointer = p->item->util;
 123                                 if (cur_depth >= *pointer)
 124                                         continue;
 125                                 *pointer = cur_depth;
 126                         }
 127                         if (p->next)
 128                                 add_object_array(&p->item->object,
 129                                                 NULL, &stack);
 130                         else {
 131                                 commit = p->item;
 132                                 cur_depth = *(int *)commit->util;
 133                         }
 134                 }
 135         }
 136
 137         return result;
 138 }
 139
 140 static void check_shallow_file_for_update(void)
 141 {
 142         if (is_shallow == -1)
 143                 die("BUG: shallow must be initialized by now");
 144
 145         if (!stat_validity_check(&shallow_stat, git_path_shallow()))
 146                 die("shallow file has changed since we read it");
 147 }
 148
 149 #define SEEN_ONLY 1
 150 #define VERBOSE   2
 151
 152 struct write_shallow_data {
 153         struct strbuf *out;
 154         int use_pack_protocol;
 155         int count;
 156         unsigned flags;
 157 };
 158
 159 static int write_one_shallow(const struct commit_graft *graft, void *cb_data)
 160 {
 161         struct write_shallow_data *data = cb_data;
 162         const char *hex = oid_to_hex(&graft->oid);
 163         if (graft->nr_parent != -1)
 164                 return 0;
 165         if (data->flags & SEEN_ONLY) {
 166                 struct commit *c = lookup_commit(graft->oid.hash);
 167                 if (!c || !(c->object.flags & SEEN)) {
 168                         if (data->flags & VERBOSE)
 169                                 printf("Removing %s from .git/shallow\n",
 170                                        sha1_to_hex(c->object.sha1));
 171                         return 0;
 172                 }
 173         }
 174         data->count++;
 175         if (data->use_pack_protocol)
 176                 packet_buf_write(data->out, "shallow %s", hex);
 177         else {
 178                 strbuf_addstr(data->out, hex);
 179                 strbuf_addch(data->out, '\n');
 180         }
 181         return 0;
 182 }
 183
 184 static int write_shallow_commits_1(struct strbuf *out, int use_pack_protocol,
 185                                    const struct sha1_array *extra,
 186                                    unsigned flags)
 187 {
 188         struct write_shallow_data data;
 189         int i;
 190         data.out = out;
 191         data.use_pack_protocol = use_pack_protocol;
 192         data.count = 0;
 193         data.flags = flags;
 194         for_each_commit_graft(write_one_shallow, &data);
 195         if (!extra)
 196                 return data.count;
 197         for (i = 0; i < extra->nr; i++) {
 198                 strbuf_addstr(out, sha1_to_hex(extra->sha1[i]));
 199                 strbuf_addch(out, '\n');
 200                 data.count++;
 201         }
 202         return data.count;
 203 }
 204
 205 int write_shallow_commits(struct strbuf *out, int use_pack_protocol,
 206                           const struct sha1_array *extra)
 207 {
 208         return write_shallow_commits_1(out, use_pack_protocol, extra, 0);
 209 }
 210
 211 static struct tempfile temporary_shallow;
 212
 213 const char *setup_temporary_shallow(const struct sha1_array *extra)
 214 {
 215         struct strbuf sb = STRBUF_INIT;
 216         int fd;
 217
 218         if (write_shallow_commits(&sb, 0, extra)) {
 219                 fd = xmks_tempfile(&temporary_shallow, git_path("shallow_XXXXXX"));
 220
 221                 if (write_in_full(fd, sb.buf, sb.len) != sb.len)
 222                         die_errno("failed to write to %s",
 223                                   get_tempfile_path(&temporary_shallow));
 224                 close_tempfile(&temporary_shallow);
 225                 strbuf_release(&sb);
 226                 return get_tempfile_path(&temporary_shallow);
 227         }
 228         /*
 229          * is_repository_shallow() sees empty string as "no shallow
 230          * file".
 231          */
 232         return get_tempfile_path(&temporary_shallow);
 233 }
 234
 235 void setup_alternate_shallow(struct lock_file *shallow_lock,
 236                              const char **alternate_shallow_file,
 237                              const struct sha1_array *extra)
 238 {
 239         struct strbuf sb = STRBUF_INIT;
 240         int fd;
 241
 242         fd = hold_lock_file_for_update(shallow_lock, git_path_shallow(),
 243                                        LOCK_DIE_ON_ERROR);
 244         check_shallow_file_for_update();
 245         if (write_shallow_commits(&sb, 0, extra)) {
 246                 if (write_in_full(fd, sb.buf, sb.len) != sb.len)
 247                         die_errno("failed to write to %s",
 248                                   get_lock_file_path(shallow_lock));
 249                 *alternate_shallow_file = get_lock_file_path(shallow_lock);
 250         } else
 251                 /*
 252                  * is_repository_shallow() sees empty string as "no
 253                  * shallow file".
 254                  */
 255                 *alternate_shallow_file = "";
 256         strbuf_release(&sb);
 257 }
 258
 259 static int advertise_shallow_grafts_cb(const struct commit_graft *graft, void *cb)
 260 {
 261         int fd = *(int *)cb;
 262         if (graft->nr_parent == -1)
 263                 packet_write(fd, "shallow %s\n", oid_to_hex(&graft->oid));
 264         return 0;
 265 }
 266
 267 void advertise_shallow_grafts(int fd)
 268 {
 269         if (!is_repository_shallow())
 270                 return;
 271         for_each_commit_graft(advertise_shallow_grafts_cb, &fd);
 272 }
 273
 274 /*
 275  * mark_reachable_objects() should have been run prior to this and all
 276  * reachable commits marked as "SEEN".
 277  */
 278 void prune_shallow(int show_only)
 279 {
 280         static struct lock_file shallow_lock;
 281         struct strbuf sb = STRBUF_INIT;
 282         int fd;
 283
 284         if (show_only) {
 285                 write_shallow_commits_1(&sb, 0, NULL, SEEN_ONLY | VERBOSE);
 286                 strbuf_release(&sb);
 287                 return;
 288         }
 289         fd = hold_lock_file_for_update(&shallow_lock, git_path_shallow(),
 290                                        LOCK_DIE_ON_ERROR);
 291         check_shallow_file_for_update();
 292         if (write_shallow_commits_1(&sb, 0, NULL, SEEN_ONLY)) {
 293                 if (write_in_full(fd, sb.buf, sb.len) != sb.len)
 294                         die_errno("failed to write to %s",
 295                                   get_lock_file_path(&shallow_lock));
 296                 commit_lock_file(&shallow_lock);
 297         } else {
 298                 unlink(git_path_shallow());
 299                 rollback_lock_file(&shallow_lock);
 300         }
 301         strbuf_release(&sb);
 302 }
 303
 304 struct trace_key trace_shallow = TRACE_KEY_INIT(SHALLOW);
 305
 306 /*
 307  * Step 1, split sender shallow commits into "ours" and "theirs"
 308  * Step 2, clean "ours" based on .git/shallow
 309  */
 310 void prepare_shallow_info(struct shallow_info *info, struct sha1_array *sa)
 311 {
 312         int i;
 313         trace_printf_key(&trace_shallow, "shallow: prepare_shallow_info\n");
 314         memset(info, 0, sizeof(*info));
 315         info->shallow = sa;
 316         if (!sa)
 317                 return;
 318         info->ours = xmalloc(sizeof(*info->ours) * sa->nr);
 319         info->theirs = xmalloc(sizeof(*info->theirs) * sa->nr);
 320         for (i = 0; i < sa->nr; i++) {
 321                 if (has_sha1_file(sa->sha1[i])) {
 322                         struct commit_graft *graft;
 323                         graft = lookup_commit_graft(sa->sha1[i]);
 324                         if (graft && graft->nr_parent < 0)
 325                                 continue;
 326                         info->ours[info->nr_ours++] = i;
 327                 } else
 328                         info->theirs[info->nr_theirs++] = i;
 329         }
 330 }
 331
 332 void clear_shallow_info(struct shallow_info *info)
 333 {
 334         free(info->ours);
 335         free(info->theirs);
 336 }
 337
 338 /* Step 4, remove non-existent ones in "theirs" after getting the pack */
 339
 340 void remove_nonexistent_theirs_shallow(struct shallow_info *info)
 341 {
 342         unsigned char (*sha1)[20] = info->shallow->sha1;
 343         int i, dst;
 344         trace_printf_key(&trace_shallow, "shallow: remove_nonexistent_theirs_shallow\n");
 345         for (i = dst = 0; i < info->nr_theirs; i++) {
 346                 if (i != dst)
 347                         info->theirs[dst] = info->theirs[i];
 348                 if (has_sha1_file(sha1[info->theirs[i]]))
 349                         dst++;
 350         }
 351         info->nr_theirs = dst;
 352 }
 353
 354 define_commit_slab(ref_bitmap, uint32_t *);
 355
 356 struct paint_info {
 357         struct ref_bitmap ref_bitmap;
 358         unsigned nr_bits;
 359         char **slab;
 360         char *free, *end;
 361         unsigned slab_count;
 362 };
 363
 364 static uint32_t *paint_alloc(struct paint_info *info)
 365 {
 366         unsigned nr = (info->nr_bits + 31) / 32;
 367         unsigned size = nr * sizeof(uint32_t);
 368         void *p;
 369         if (!info->slab_count || info->free + size > info->end) {
 370                 info->slab_count++;
 371                 REALLOC_ARRAY(info->slab, info->slab_count);
 372                 info->free = xmalloc(COMMIT_SLAB_SIZE);
 373                 info->slab[info->slab_count - 1] = info->free;
 374                 info->end = info->free + COMMIT_SLAB_SIZE;
 375         }
 376         p = info->free;
 377         info->free += size;
 378         return p;
 379 }
 380
 381 /*
 382  * Given a commit SHA-1, walk down to parents until either SEEN,
 383  * UNINTERESTING or BOTTOM is hit. Set the id-th bit in ref_bitmap for
 384  * all walked commits.
 385  */
 386 static void paint_down(struct paint_info *info, const unsigned char *sha1,
 387                        int id)
 388 {
 389         unsigned int i, nr;
 390         struct commit_list *head = NULL;
 391         int bitmap_nr = (info->nr_bits + 31) / 32;
 392         int bitmap_size = bitmap_nr * sizeof(uint32_t);
 393         uint32_t *tmp = xmalloc(bitmap_size); /* to be freed before return */
 394         uint32_t *bitmap = paint_alloc(info);
 395         struct commit *c = lookup_commit_reference_gently(sha1, 1);
 396         if (!c)
 397                 return;
 398         memset(bitmap, 0, bitmap_size);
 399         bitmap[id / 32] |= (1 << (id % 32));
 400         commit_list_insert(c, &head);
 401         while (head) {
 402                 struct commit_list *p;
 403                 struct commit *c = head->item;
 404                 uint32_t **refs = ref_bitmap_at(&info->ref_bitmap, c);
 405
 406                 p = head;
 407                 head = head->next;
 408                 free(p);
 409
 410                 /* XXX check "UNINTERESTING" from pack bitmaps if available */
 411                 if (c->object.flags & (SEEN | UNINTERESTING))
 412                         continue;
 413                 else
 414                         c->object.flags |= SEEN;
 415
 416                 if (*refs == NULL)
 417                         *refs = bitmap;
 418                 else {
 419                         memcpy(tmp, *refs, bitmap_size);
 420                         for (i = 0; i < bitmap_nr; i++)
 421                                 tmp[i] |= bitmap[i];
 422                         if (memcmp(tmp, *refs, bitmap_size)) {
 423                                 *refs = paint_alloc(info);
 424                                 memcpy(*refs, tmp, bitmap_size);
 425                         }
 426                 }
 427
 428                 if (c->object.flags & BOTTOM)
 429                         continue;
 430
 431                 if (parse_commit(c))
 432                         die("unable to parse commit %s",
 433                             sha1_to_hex(c->object.sha1));
 434
 435                 for (p = c->parents; p; p = p->next) {
 436                         uint32_t **p_refs = ref_bitmap_at(&info->ref_bitmap,
 437                                                           p->item);
 438                         if (p->item->object.flags & SEEN)
 439                                 continue;
 440                         if (*p_refs == NULL || *p_refs == *refs)
 441                                 *p_refs = *refs;
 442                         commit_list_insert(p->item, &head);
 443                 }
 444         }
 445
 446         nr = get_max_object_index();
 447         for (i = 0; i < nr; i++) {
 448                 struct object *o = get_indexed_object(i);
 449                 if (o && o->type == OBJ_COMMIT)
 450                         o->flags &= ~SEEN;
 451         }
 452
 453         free(tmp);
 454 }
 455
 456 static int mark_uninteresting(const char *refname, const struct object_id *oid,
 457                               int flags, void *cb_data)
 458 {
 459         struct commit *commit = lookup_commit_reference_gently(oid->hash, 1);
 460         if (!commit)
 461                 return 0;
 462         commit->object.flags |= UNINTERESTING;
 463         mark_parents_uninteresting(commit);
 464         return 0;
 465 }
 466
 467 static void post_assign_shallow(struct shallow_info *info,
 468                                 struct ref_bitmap *ref_bitmap,
 469                                 int *ref_status);
 470 /*
 471  * Step 6(+7), associate shallow commits with new refs
 472  *
 473  * info->ref must be initialized before calling this function.
 474  *
 475  * If used is not NULL, it's an array of info->shallow->nr
 476  * bitmaps. The n-th bit set in the m-th bitmap if ref[n] needs the
 477  * m-th shallow commit from info->shallow.
 478  *
 479  * If used is NULL, "ours" and "theirs" are updated. And if ref_status
 480  * is not NULL it's an array of ref->nr ints. ref_status[i] is true if
 481  * the ref needs some shallow commits from either info->ours or
 482  * info->theirs.
 483  */
 484 void assign_shallow_commits_to_refs(struct shallow_info *info,
 485                                     uint32_t **used, int *ref_status)
 486 {
 487         unsigned char (*sha1)[20] = info->shallow->sha1;
 488         struct sha1_array *ref = info->ref;
 489         unsigned int i, nr;
 490         int *shallow, nr_shallow = 0;
 491         struct paint_info pi;
 492
 493         trace_printf_key(&trace_shallow, "shallow: assign_shallow_commits_to_refs\n");
 494         shallow = xmalloc(sizeof(*shallow) * (info->nr_ours + info->nr_theirs));
 495         for (i = 0; i < info->nr_ours; i++)
 496                 shallow[nr_shallow++] = info->ours[i];
 497         for (i = 0; i < info->nr_theirs; i++)
 498                 shallow[nr_shallow++] = info->theirs[i];
 499
 500         /*
 501          * Prepare the commit graph to track what refs can reach what
 502          * (new) shallow commits.
 503          */
 504         nr = get_max_object_index();
 505         for (i = 0; i < nr; i++) {
 506                 struct object *o = get_indexed_object(i);
 507                 if (!o || o->type != OBJ_COMMIT)
 508                         continue;
 509
 510                 o->flags &= ~(UNINTERESTING | BOTTOM | SEEN);
 511         }
 512
 513         memset(&pi, 0, sizeof(pi));
 514         init_ref_bitmap(&pi.ref_bitmap);
 515         pi.nr_bits = ref->nr;
 516
 517         /*
 518          * "--not --all" to cut short the traversal if new refs
 519          * connect to old refs. If not (e.g. force ref updates) it'll
 520          * have to go down to the current shallow commits.
 521          */
 522         head_ref(mark_uninteresting, NULL);
 523         for_each_ref(mark_uninteresting, NULL);
 524
 525         /* Mark potential bottoms so we won't go out of bound */
 526         for (i = 0; i < nr_shallow; i++) {
 527                 struct commit *c = lookup_commit(sha1[shallow[i]]);
 528                 c->object.flags |= BOTTOM;
 529         }
 530
 531         for (i = 0; i < ref->nr; i++)
 532                 paint_down(&pi, ref->sha1[i], i);
 533
 534         if (used) {
 535                 int bitmap_size = ((pi.nr_bits + 31) / 32) * sizeof(uint32_t);
 536                 memset(used, 0, sizeof(*used) * info->shallow->nr);
 537                 for (i = 0; i < nr_shallow; i++) {
 538                         const struct commit *c = lookup_commit(sha1[shallow[i]]);
 539                         uint32_t **map = ref_bitmap_at(&pi.ref_bitmap, c);
 540                         if (*map)
 541                                 used[shallow[i]] = xmemdupz(*map, bitmap_size);
 542                 }
 543                 /*
 544                  * unreachable shallow commits are not removed from
 545                  * "ours" and "theirs". The user is supposed to run
 546                  * step 7 on every ref separately and not trust "ours"
 547                  * and "theirs" any more.
 548                  */
 549         } else
 550                 post_assign_shallow(info, &pi.ref_bitmap, ref_status);
 551
 552         clear_ref_bitmap(&pi.ref_bitmap);
 553         for (i = 0; i < pi.slab_count; i++)
 554                 free(pi.slab[i]);
 555         free(pi.slab);
 556         free(shallow);
 557 }
 558
 559 struct commit_array {
 560         struct commit **commits;
 561         int nr, alloc;
 562 };
 563
 564 static int add_ref(const char *refname, const struct object_id *oid,
 565                    int flags, void *cb_data)
 566 {
 567         struct commit_array *ca = cb_data;
 568         ALLOC_GROW(ca->commits, ca->nr + 1, ca->alloc);
 569         ca->commits[ca->nr] = lookup_commit_reference_gently(oid->hash, 1);
 570         if (ca->commits[ca->nr])
 571                 ca->nr++;
 572         return 0;
 573 }
 574
 575 static void update_refstatus(int *ref_status, int nr, uint32_t *bitmap)
 576 {
 577         int i;
 578         if (!ref_status)
 579                 return;
 580         for (i = 0; i < nr; i++)
 581                 if (bitmap[i / 32] & (1 << (i % 32)))
 582                         ref_status[i]++;
 583 }
 584
 585 /*
 586  * Step 7, reachability test on "ours" at commit level
 587  */
 588 static void post_assign_shallow(struct shallow_info *info,
 589                                 struct ref_bitmap *ref_bitmap,
 590                                 int *ref_status)
 591 {
 592         unsigned char (*sha1)[20] = info->shallow->sha1;
 593         struct commit *c;
 594         uint32_t **bitmap;
 595         int dst, i, j;
 596         int bitmap_nr = (info->ref->nr + 31) / 32;
 597         struct commit_array ca;
 598
 599         trace_printf_key(&trace_shallow, "shallow: post_assign_shallow\n");
 600         if (ref_status)
 601                 memset(ref_status, 0, sizeof(*ref_status) * info->ref->nr);
 602
 603         /* Remove unreachable shallow commits from "theirs" */
 604         for (i = dst = 0; i < info->nr_theirs; i++) {
 605                 if (i != dst)
 606                         info->theirs[dst] = info->theirs[i];
 607                 c = lookup_commit(sha1[info->theirs[i]]);
 608                 bitmap = ref_bitmap_at(ref_bitmap, c);
 609                 if (!*bitmap)
 610                         continue;
 611                 for (j = 0; j < bitmap_nr; j++)
 612                         if (bitmap[0][j]) {
 613                                 update_refstatus(ref_status, info->ref->nr, *bitmap);
 614                                 dst++;
 615                                 break;
 616                         }
 617         }
 618         info->nr_theirs = dst;
 619
 620         memset(&ca, 0, sizeof(ca));
 621         head_ref(add_ref, &ca);
 622         for_each_ref(add_ref, &ca);
 623
 624         /* Remove unreachable shallow commits from "ours" */
 625         for (i = dst = 0; i < info->nr_ours; i++) {
 626                 if (i != dst)
 627                         info->ours[dst] = info->ours[i];
 628                 c = lookup_commit(sha1[info->ours[i]]);
 629                 bitmap = ref_bitmap_at(ref_bitmap, c);
 630                 if (!*bitmap)
 631                         continue;
 632                 for (j = 0; j < bitmap_nr; j++)
 633                         if (bitmap[0][j] &&
 634                             /* Step 7, reachability test at commit level */
 635                             !in_merge_bases_many(c, ca.nr, ca.commits)) {
 636                                 update_refstatus(ref_status, info->ref->nr, *bitmap);
 637                                 dst++;
 638                                 break;
 639                         }
 640         }
 641         info->nr_ours = dst;
 642
 643         free(ca.commits);
 644 }
 645
 646 /* (Delayed) step 7, reachability test at commit level */
 647 int delayed_reachability_test(struct shallow_info *si, int c)
 648 {
 649         if (si->need_reachability_test[c]) {
 650                 struct commit *commit = lookup_commit(si->shallow->sha1[c]);
 651
 652                 if (!si->commits) {
 653                         struct commit_array ca;
 654
 655                         memset(&ca, 0, sizeof(ca));
 656                         head_ref(add_ref, &ca);
 657                         for_each_ref(add_ref, &ca);
 658                         si->commits = ca.commits;
 659                         si->nr_commits = ca.nr;
 660                 }
 661
 662                 si->reachable[c] = in_merge_bases_many(commit,
 663                                                        si->nr_commits,
 664                                                        si->commits);
 665                 si->need_reachability_test[c] = 0;
 666         }
 667         return si->reachable[c];
 668 }