refs.c

   1 #include "refs.h"
   2 #include "cache.h"
   3
   4 #include <errno.h>
   5
   6 struct ref_list {
   7         struct ref_list *next;
   8         unsigned char flag; /* ISSYMREF? ISPACKED? */
   9         unsigned char sha1[20];
  10         char name[FLEX_ARRAY];
  11 };
  12
  13 static const char *parse_ref_line(char *line, unsigned char *sha1)
  14 {
  15         /*
  16          * 42: the answer to everything.
  17          *
  18          * In this case, it happens to be the answer to
  19          *  40 (length of sha1 hex representation)
  20          *  +1 (space in between hex and name)
  21          *  +1 (newline at the end of the line)
  22          */
  23         int len = strlen(line) - 42;
  24
  25         if (len <= 0)
  26                 return NULL;
  27         if (get_sha1_hex(line, sha1) < 0)
  28                 return NULL;
  29         if (!isspace(line[40]))
  30                 return NULL;
  31         line += 41;
  32         if (isspace(*line))
  33                 return NULL;
  34         if (line[len] != '\n')
  35                 return NULL;
  36         line[len] = 0;
  37         return line;
  38 }
  39
  40 static struct ref_list *add_ref(const char *name, const unsigned char *sha1,
  41                                 int flag, struct ref_list *list)
  42 {
  43         int len;
  44         struct ref_list **p = &list, *entry;
  45
  46         /* Find the place to insert the ref into.. */
  47         while ((entry = *p) != NULL) {
  48                 int cmp = strcmp(entry->name, name);
  49                 if (cmp > 0)
  50                         break;
  51
  52                 /* Same as existing entry? */
  53                 if (!cmp)
  54                         return list;
  55                 p = &entry->next;
  56         }
  57
  58         /* Allocate it and add it in.. */
  59         len = strlen(name) + 1;
  60         entry = xmalloc(sizeof(struct ref_list) + len);
  61         hashcpy(entry->sha1, sha1);
  62         memcpy(entry->name, name, len);
  63         entry->flag = flag;
  64         entry->next = *p;
  65         *p = entry;
  66         return list;
  67 }
  68
  69 /*
  70  * Future: need to be in "struct repository"
  71  * when doing a full libification.
  72  */
  73 struct cached_refs {
  74         char did_loose;
  75         char did_packed;
  76         struct ref_list *loose;
  77         struct ref_list *packed;
  78 } cached_refs;
  79
  80 static void free_ref_list(struct ref_list *list)
  81 {
  82         struct ref_list *next;
  83         for ( ; list; list = next) {
  84                 next = list->next;
  85                 free(list);
  86         }
  87 }
  88
  89 static void invalidate_cached_refs(void)
  90 {
  91         struct cached_refs *ca = &cached_refs;
  92
  93         if (ca->did_loose && ca->loose)
  94                 free_ref_list(ca->loose);
  95         if (ca->did_packed && ca->packed)
  96                 free_ref_list(ca->packed);
  97         ca->loose = ca->packed = NULL;
  98         ca->did_loose = ca->did_packed = 0;
  99 }
 100
 101 static struct ref_list *get_packed_refs(void)
 102 {
 103         if (!cached_refs.did_packed) {
 104                 struct ref_list *refs = NULL;
 105                 FILE *f = fopen(git_path("packed-refs"), "r");
 106                 if (f) {
 107                         struct ref_list *list = NULL;
 108                         char refline[PATH_MAX];
 109                         while (fgets(refline, sizeof(refline), f)) {
 110                                 unsigned char sha1[20];
 111                                 const char *name = parse_ref_line(refline, sha1);
 112                                 if (!name)
 113                                         continue;
 114                                 list = add_ref(name, sha1, REF_ISPACKED, list);
 115                         }
 116                         fclose(f);
 117                         refs = list;
 118                 }
 119                 cached_refs.packed = refs;
 120                 cached_refs.did_packed = 1;
 121         }
 122         return cached_refs.packed;
 123 }
 124
 125 static struct ref_list *get_ref_dir(const char *base, struct ref_list *list)
 126 {
 127         DIR *dir = opendir(git_path("%s", base));
 128
 129         if (dir) {
 130                 struct dirent *de;
 131                 int baselen = strlen(base);
 132                 char *ref = xmalloc(baselen + 257);
 133
 134                 memcpy(ref, base, baselen);
 135                 if (baselen && base[baselen-1] != '/')
 136                         ref[baselen++] = '/';
 137
 138                 while ((de = readdir(dir)) != NULL) {
 139                         unsigned char sha1[20];
 140                         struct stat st;
 141                         int flag;
 142                         int namelen;
 143
 144                         if (de->d_name[0] == '.')
 145                                 continue;
 146                         namelen = strlen(de->d_name);
 147                         if (namelen > 255)
 148                                 continue;
 149                         if (has_extension(de->d_name, ".lock"))
 150                                 continue;
 151                         memcpy(ref + baselen, de->d_name, namelen+1);
 152                         if (stat(git_path("%s", ref), &st) < 0)
 153                                 continue;
 154                         if (S_ISDIR(st.st_mode)) {
 155                                 list = get_ref_dir(ref, list);
 156                                 continue;
 157                         }
 158                         if (!resolve_ref(ref, sha1, 1, &flag)) {
 159                                 error("%s points nowhere!", ref);
 160                                 continue;
 161                         }
 162                         list = add_ref(ref, sha1, flag, list);
 163                 }
 164                 free(ref);
 165                 closedir(dir);
 166         }
 167         return list;
 168 }
 169
 170 static struct ref_list *get_loose_refs(void)
 171 {
 172         if (!cached_refs.did_loose) {
 173                 cached_refs.loose = get_ref_dir("refs", NULL);
 174                 cached_refs.did_loose = 1;
 175         }
 176         return cached_refs.loose;
 177 }
 178
 179 /* We allow "recursive" symbolic refs. Only within reason, though */
 180 #define MAXDEPTH 5
 181
 182 const char *resolve_ref(const char *ref, unsigned char *sha1, int reading, int *flag)
 183 {
 184         int depth = MAXDEPTH, len;
 185         char buffer[256];
 186         static char ref_buffer[256];
 187
 188         if (flag)
 189                 *flag = 0;
 190
 191         for (;;) {
 192                 const char *path = git_path("%s", ref);
 193                 struct stat st;
 194                 char *buf;
 195                 int fd;
 196
 197                 if (--depth < 0)
 198                         return NULL;
 199
 200                 /* Special case: non-existing file.
 201                  * Not having the refs/heads/new-branch is OK
 202                  * if we are writing into it, so is .git/HEAD
 203                  * that points at refs/heads/master still to be
 204                  * born.  It is NOT OK if we are resolving for
 205                  * reading.
 206                  */
 207                 if (lstat(path, &st) < 0) {
 208                         struct ref_list *list = get_packed_refs();
 209                         while (list) {
 210                                 if (!strcmp(ref, list->name)) {
 211                                         hashcpy(sha1, list->sha1);
 212                                         if (flag)
 213                                                 *flag |= REF_ISPACKED;
 214                                         return ref;
 215                                 }
 216                                 list = list->next;
 217                         }
 218                         if (reading || errno != ENOENT)
 219                                 return NULL;
 220                         hashclr(sha1);
 221                         return ref;
 222                 }
 223
 224                 /* Follow "normalized" - ie "refs/.." symlinks by hand */
 225                 if (S_ISLNK(st.st_mode)) {
 226                         len = readlink(path, buffer, sizeof(buffer)-1);
 227                         if (len >= 5 && !memcmp("refs/", buffer, 5)) {
 228                                 buffer[len] = 0;
 229                                 strcpy(ref_buffer, buffer);
 230                                 ref = ref_buffer;
 231                                 if (flag)
 232                                         *flag |= REF_ISSYMREF;
 233                                 continue;
 234                         }
 235                 }
 236
 237                 /* Is it a directory? */
 238                 if (S_ISDIR(st.st_mode)) {
 239                         errno = EISDIR;
 240                         return NULL;
 241                 }
 242
 243                 /*
 244                  * Anything else, just open it and try to use it as
 245                  * a ref
 246                  */
 247                 fd = open(path, O_RDONLY);
 248                 if (fd < 0)
 249                         return NULL;
 250                 len = read(fd, buffer, sizeof(buffer)-1);
 251                 close(fd);
 252
 253                 /*
 254                  * Is it a symbolic ref?
 255                  */
 256                 if (len < 4 || memcmp("ref:", buffer, 4))
 257                         break;
 258                 buf = buffer + 4;
 259                 len -= 4;
 260                 while (len && isspace(*buf))
 261                         buf++, len--;
 262                 while (len && isspace(buf[len-1]))
 263                         len--;
 264                 buf[len] = 0;
 265                 memcpy(ref_buffer, buf, len + 1);
 266                 ref = ref_buffer;
 267                 if (flag)
 268                         *flag |= REF_ISSYMREF;
 269         }
 270         if (len < 40 || get_sha1_hex(buffer, sha1))
 271                 return NULL;
 272         return ref;
 273 }
 274
 275 int create_symref(const char *ref_target, const char *refs_heads_master)
 276 {
 277         const char *lockpath;
 278         char ref[1000];
 279         int fd, len, written;
 280         const char *git_HEAD = git_path("%s", ref_target);
 281
 282 #ifndef NO_SYMLINK_HEAD
 283         if (prefer_symlink_refs) {
 284                 unlink(git_HEAD);
 285                 if (!symlink(refs_heads_master, git_HEAD))
 286                         return 0;
 287                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
 288         }
 289 #endif
 290
 291         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
 292         if (sizeof(ref) <= len) {
 293                 error("refname too long: %s", refs_heads_master);
 294                 return -1;
 295         }
 296         lockpath = mkpath("%s.lock", git_HEAD);
 297         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
 298         written = write(fd, ref, len);
 299         close(fd);
 300         if (written != len) {
 301                 unlink(lockpath);
 302                 error("Unable to write to %s", lockpath);
 303                 return -2;
 304         }
 305         if (rename(lockpath, git_HEAD) < 0) {
 306                 unlink(lockpath);
 307                 error("Unable to create %s", git_HEAD);
 308                 return -3;
 309         }
 310         if (adjust_shared_perm(git_HEAD)) {
 311                 unlink(lockpath);
 312                 error("Unable to fix permissions on %s", lockpath);
 313                 return -4;
 314         }
 315         return 0;
 316 }
 317
 318 int read_ref(const char *ref, unsigned char *sha1)
 319 {
 320         if (resolve_ref(ref, sha1, 1, NULL))
 321                 return 0;
 322         return -1;
 323 }
 324
 325 static int do_for_each_ref(const char *base, each_ref_fn fn, int trim,
 326                            void *cb_data)
 327 {
 328         int retval;
 329         struct ref_list *packed = get_packed_refs();
 330         struct ref_list *loose = get_loose_refs();
 331
 332         while (packed && loose) {
 333                 struct ref_list *entry;
 334                 int cmp = strcmp(packed->name, loose->name);
 335                 if (!cmp) {
 336                         packed = packed->next;
 337                         continue;
 338                 }
 339                 if (cmp > 0) {
 340                         entry = loose;
 341                         loose = loose->next;
 342                 } else {
 343                         entry = packed;
 344                         packed = packed->next;
 345                 }
 346                 if (strncmp(base, entry->name, trim))
 347                         continue;
 348                 if (is_null_sha1(entry->sha1))
 349                         continue;
 350                 if (!has_sha1_file(entry->sha1)) {
 351                         error("%s does not point to a valid object!", entry->name);
 352                         continue;
 353                 }
 354                 retval = fn(entry->name + trim, entry->sha1,
 355                             entry->flag, cb_data);
 356                 if (retval)
 357                         return retval;
 358         }
 359
 360         packed = packed ? packed : loose;
 361         while (packed) {
 362                 if (!strncmp(base, packed->name, trim)) {
 363                         retval = fn(packed->name + trim, packed->sha1,
 364                                     packed->flag, cb_data);
 365                         if (retval)
 366                                 return retval;
 367                 }
 368                 packed = packed->next;
 369         }
 370         return 0;
 371 }
 372
 373 int head_ref(each_ref_fn fn, void *cb_data)
 374 {
 375         unsigned char sha1[20];
 376         int flag;
 377
 378         if (resolve_ref("HEAD", sha1, 1, &flag))
 379                 return fn("HEAD", sha1, flag, cb_data);
 380         return 0;
 381 }
 382
 383 int for_each_ref(each_ref_fn fn, void *cb_data)
 384 {
 385         return do_for_each_ref("refs/", fn, 0, cb_data);
 386 }
 387
 388 int for_each_tag_ref(each_ref_fn fn, void *cb_data)
 389 {
 390         return do_for_each_ref("refs/tags/", fn, 10, cb_data);
 391 }
 392
 393 int for_each_branch_ref(each_ref_fn fn, void *cb_data)
 394 {
 395         return do_for_each_ref("refs/heads/", fn, 11, cb_data);
 396 }
 397
 398 int for_each_remote_ref(each_ref_fn fn, void *cb_data)
 399 {
 400         return do_for_each_ref("refs/remotes/", fn, 13, cb_data);
 401 }
 402
 403 /* NEEDSWORK: This is only used by ssh-upload and it should go; the
 404  * caller should do resolve_ref or read_ref like everybody else.  Or
 405  * maybe everybody else should use get_ref_sha1() instead of doing
 406  * read_ref().
 407  */
 408 int get_ref_sha1(const char *ref, unsigned char *sha1)
 409 {
 410         if (check_ref_format(ref))
 411                 return -1;
 412         return read_ref(mkpath("refs/%s", ref), sha1);
 413 }
 414
 415 /*
 416  * Make sure "ref" is something reasonable to have under ".git/refs/";
 417  * We do not like it if:
 418  *
 419  * - any path component of it begins with ".", or
 420  * - it has double dots "..", or
 421  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 422  * - it ends with a "/".
 423  */
 424
 425 static inline int bad_ref_char(int ch)
 426 {
 427         return (((unsigned) ch) <= ' ' ||
 428                 ch == '~' || ch == '^' || ch == ':' ||
 429                 /* 2.13 Pattern Matching Notation */
 430                 ch == '?' || ch == '*' || ch == '[');
 431 }
 432
 433 int check_ref_format(const char *ref)
 434 {
 435         int ch, level;
 436         const char *cp = ref;
 437
 438         level = 0;
 439         while (1) {
 440                 while ((ch = *cp++) == '/')
 441                         ; /* tolerate duplicated slashes */
 442                 if (!ch)
 443                         return -1; /* should not end with slashes */
 444
 445                 /* we are at the beginning of the path component */
 446                 if (ch == '.' || bad_ref_char(ch))
 447                         return -1;
 448
 449                 /* scan the rest of the path component */
 450                 while ((ch = *cp++) != 0) {
 451                         if (bad_ref_char(ch))
 452                                 return -1;
 453                         if (ch == '/')
 454                                 break;
 455                         if (ch == '.' && *cp == '.')
 456                                 return -1;
 457                 }
 458                 level++;
 459                 if (!ch) {
 460                         if (level < 2)
 461                                 return -1; /* at least of form "heads/blah" */
 462                         return 0;
 463                 }
 464         }
 465 }
 466
 467 static struct ref_lock *verify_lock(struct ref_lock *lock,
 468         const unsigned char *old_sha1, int mustexist)
 469 {
 470         if (!resolve_ref(lock->ref_name, lock->old_sha1, mustexist, NULL)) {
 471                 error("Can't verify ref %s", lock->ref_name);
 472                 unlock_ref(lock);
 473                 return NULL;
 474         }
 475         if (hashcmp(lock->old_sha1, old_sha1)) {
 476                 error("Ref %s is at %s but expected %s", lock->ref_name,
 477                         sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
 478                 unlock_ref(lock);
 479                 return NULL;
 480         }
 481         return lock;
 482 }
 483
 484 static int remove_empty_dir_recursive(char *path, int len)
 485 {
 486         DIR *dir = opendir(path);
 487         struct dirent *e;
 488         int ret = 0;
 489
 490         if (!dir)
 491                 return -1;
 492         if (path[len-1] != '/')
 493                 path[len++] = '/';
 494         while ((e = readdir(dir)) != NULL) {
 495                 struct stat st;
 496                 int namlen;
 497                 if ((e->d_name[0] == '.') &&
 498                     ((e->d_name[1] == 0) ||
 499                      ((e->d_name[1] == '.') && e->d_name[2] == 0)))
 500                         continue; /* "." and ".." */
 501
 502                 namlen = strlen(e->d_name);
 503                 if ((len + namlen < PATH_MAX) &&
 504                     strcpy(path + len, e->d_name) &&
 505                     !lstat(path, &st) &&
 506                     S_ISDIR(st.st_mode) &&
 507                     !remove_empty_dir_recursive(path, len + namlen))
 508                         continue; /* happy */
 509
 510                 /* path too long, stat fails, or non-directory still exists */
 511                 ret = -1;
 512                 break;
 513         }
 514         closedir(dir);
 515         if (!ret) {
 516                 path[len] = 0;
 517                 ret = rmdir(path);
 518         }
 519         return ret;
 520 }
 521
 522 static int remove_empty_directories(char *file)
 523 {
 524         /* we want to create a file but there is a directory there;
 525          * if that is an empty directory (or a directory that contains
 526          * only empty directories), remove them.
 527          */
 528         char path[PATH_MAX];
 529         int len = strlen(file);
 530
 531         if (len >= PATH_MAX) /* path too long ;-) */
 532                 return -1;
 533         strcpy(path, file);
 534         return remove_empty_dir_recursive(path, len);
 535 }
 536
 537 static struct ref_lock *lock_ref_sha1_basic(const char *ref, const unsigned char *old_sha1, int *flag)
 538 {
 539         char *ref_file;
 540         const char *orig_ref = ref;
 541         struct ref_lock *lock;
 542         struct stat st;
 543         int last_errno = 0;
 544         int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
 545
 546         lock = xcalloc(1, sizeof(struct ref_lock));
 547         lock->lock_fd = -1;
 548
 549         ref = resolve_ref(ref, lock->old_sha1, mustexist, flag);
 550         if (!ref && errno == EISDIR) {
 551                 /* we are trying to lock foo but we used to
 552                  * have foo/bar which now does not exist;
 553                  * it is normal for the empty directory 'foo'
 554                  * to remain.
 555                  */
 556                 ref_file = git_path("%s", orig_ref);
 557                 if (remove_empty_directories(ref_file)) {
 558                         last_errno = errno;
 559                         error("there are still refs under '%s'", orig_ref);
 560                         goto error_return;
 561                 }
 562                 ref = resolve_ref(orig_ref, lock->old_sha1, mustexist, flag);
 563         }
 564         if (!ref) {
 565                 last_errno = errno;
 566                 error("unable to resolve reference %s: %s",
 567                         orig_ref, strerror(errno));
 568                 goto error_return;
 569         }
 570         if (is_null_sha1(lock->old_sha1)) {
 571                 /* The ref did not exist and we are creating it.
 572                  * Make sure there is no existing ref that is packed
 573                  * whose name begins with our refname, nor a ref whose
 574                  * name is a proper prefix of our refname.
 575                  */
 576                 int namlen = strlen(ref); /* e.g. 'foo/bar' */
 577                 struct ref_list *list = get_packed_refs();
 578                 while (list) {
 579                         /* list->name could be 'foo' or 'foo/bar/baz' */
 580                         int len = strlen(list->name);
 581                         int cmplen = (namlen < len) ? namlen : len;
 582                         const char *lead = (namlen < len) ? list->name : ref;
 583
 584                         if (!strncmp(ref, list->name, cmplen) &&
 585                             lead[cmplen] == '/') {
 586                                 error("'%s' exists; cannot create '%s'",
 587                                       list->name, ref);
 588                                 goto error_return;
 589                         }
 590                         list = list->next;
 591                 }
 592         }
 593
 594         lock->lk = xcalloc(1, sizeof(struct lock_file));
 595
 596         lock->ref_name = xstrdup(ref);
 597         lock->log_file = xstrdup(git_path("logs/%s", ref));
 598         ref_file = git_path("%s", ref);
 599         lock->force_write = lstat(ref_file, &st) && errno == ENOENT;
 600
 601         if (safe_create_leading_directories(ref_file)) {
 602                 last_errno = errno;
 603                 error("unable to create directory for %s", ref_file);
 604                 goto error_return;
 605         }
 606         lock->lock_fd = hold_lock_file_for_update(lock->lk, ref_file, 1);
 607
 608         return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
 609
 610  error_return:
 611         unlock_ref(lock);
 612         errno = last_errno;
 613         return NULL;
 614 }
 615
 616 struct ref_lock *lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 617 {
 618         char refpath[PATH_MAX];
 619         if (check_ref_format(ref))
 620                 return NULL;
 621         strcpy(refpath, mkpath("refs/%s", ref));
 622         return lock_ref_sha1_basic(refpath, old_sha1, NULL);
 623 }
 624
 625 struct ref_lock *lock_any_ref_for_update(const char *ref, const unsigned char *old_sha1)
 626 {
 627         return lock_ref_sha1_basic(ref, old_sha1, NULL);
 628 }
 629
 630 static struct lock_file packlock;
 631
 632 static int repack_without_ref(const char *refname)
 633 {
 634         struct ref_list *list, *packed_ref_list;
 635         int fd;
 636         int found = 0;
 637
 638         packed_ref_list = get_packed_refs();
 639         for (list = packed_ref_list; list; list = list->next) {
 640                 if (!strcmp(refname, list->name)) {
 641                         found = 1;
 642                         break;
 643                 }
 644         }
 645         if (!found)
 646                 return 0;
 647         memset(&packlock, 0, sizeof(packlock));
 648         fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"), 0);
 649         if (fd < 0)
 650                 return error("cannot delete '%s' from packed refs", refname);
 651
 652         for (list = packed_ref_list; list; list = list->next) {
 653                 char line[PATH_MAX + 100];
 654                 int len;
 655
 656                 if (!strcmp(refname, list->name))
 657                         continue;
 658                 len = snprintf(line, sizeof(line), "%s %s\n",
 659                                sha1_to_hex(list->sha1), list->name);
 660                 /* this should not happen but just being defensive */
 661                 if (len > sizeof(line))
 662                         die("too long a refname '%s'", list->name);
 663                 write_or_die(fd, line, len);
 664         }
 665         return commit_lock_file(&packlock);
 666 }
 667
 668 int delete_ref(const char *refname, unsigned char *sha1)
 669 {
 670         struct ref_lock *lock;
 671         int err, i, ret = 0, flag = 0;
 672
 673         lock = lock_ref_sha1_basic(refname, sha1, &flag);
 674         if (!lock)
 675                 return 1;
 676         if (!(flag & REF_ISPACKED)) {
 677                 /* loose */
 678                 i = strlen(lock->lk->filename) - 5; /* .lock */
 679                 lock->lk->filename[i] = 0;
 680                 err = unlink(lock->lk->filename);
 681                 if (err) {
 682                         ret = 1;
 683                         error("unlink(%s) failed: %s",
 684                               lock->lk->filename, strerror(errno));
 685                 }
 686                 lock->lk->filename[i] = '.';
 687         }
 688         /* removing the loose one could have resurrected an earlier
 689          * packed one.  Also, if it was not loose we need to repack
 690          * without it.
 691          */
 692         ret |= repack_without_ref(refname);
 693
 694         err = unlink(lock->log_file);
 695         if (err && errno != ENOENT)
 696                 fprintf(stderr, "warning: unlink(%s) failed: %s",
 697                         lock->log_file, strerror(errno));
 698         invalidate_cached_refs();
 699         unlock_ref(lock);
 700         return ret;
 701 }
 702
 703 void unlock_ref(struct ref_lock *lock)
 704 {
 705         if (lock->lock_fd >= 0) {
 706                 close(lock->lock_fd);
 707                 /* Do not free lock->lk -- atexit() still looks at them */
 708                 if (lock->lk)
 709                         rollback_lock_file(lock->lk);
 710         }
 711         free(lock->ref_name);
 712         free(lock->log_file);
 713         free(lock);
 714 }
 715
 716 static int log_ref_write(struct ref_lock *lock,
 717         const unsigned char *sha1, const char *msg)
 718 {
 719         int logfd, written, oflags = O_APPEND | O_WRONLY;
 720         unsigned maxlen, len;
 721         char *logrec;
 722         const char *committer;
 723
 724         if (log_all_ref_updates &&
 725             !strncmp(lock->ref_name, "refs/heads/", 11)) {
 726                 if (safe_create_leading_directories(lock->log_file) < 0)
 727                         return error("unable to create directory for %s",
 728                                 lock->log_file);
 729                 oflags |= O_CREAT;
 730         }
 731
 732         logfd = open(lock->log_file, oflags, 0666);
 733         if (logfd < 0) {
 734                 if (!(oflags & O_CREAT) && errno == ENOENT)
 735                         return 0;
 736
 737                 if ((oflags & O_CREAT) && errno == EISDIR) {
 738                         if (remove_empty_directories(lock->log_file)) {
 739                                 return error("There are still logs under '%s'",
 740                                              lock->log_file);
 741                         }
 742                         logfd = open(lock->log_file, oflags, 0666);
 743                 }
 744
 745                 if (logfd < 0)
 746                         return error("Unable to append to %s: %s",
 747                                      lock->log_file, strerror(errno));
 748         }
 749
 750         committer = git_committer_info(1);
 751         if (msg) {
 752                 maxlen = strlen(committer) + strlen(msg) + 2*40 + 5;
 753                 logrec = xmalloc(maxlen);
 754                 len = snprintf(logrec, maxlen, "%s %s %s\t%s\n",
 755                         sha1_to_hex(lock->old_sha1),
 756                         sha1_to_hex(sha1),
 757                         committer,
 758                         msg);
 759         }
 760         else {
 761                 maxlen = strlen(committer) + 2*40 + 4;
 762                 logrec = xmalloc(maxlen);
 763                 len = snprintf(logrec, maxlen, "%s %s %s\n",
 764                         sha1_to_hex(lock->old_sha1),
 765                         sha1_to_hex(sha1),
 766                         committer);
 767         }
 768         written = len <= maxlen ? write(logfd, logrec, len) : -1;
 769         free(logrec);
 770         close(logfd);
 771         if (written != len)
 772                 return error("Unable to append to %s", lock->log_file);
 773         return 0;
 774 }
 775
 776 int write_ref_sha1(struct ref_lock *lock,
 777         const unsigned char *sha1, const char *logmsg)
 778 {
 779         static char term = '\n';
 780
 781         if (!lock)
 782                 return -1;
 783         if (!lock->force_write && !hashcmp(lock->old_sha1, sha1)) {
 784                 unlock_ref(lock);
 785                 return 0;
 786         }
 787         if (write(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
 788             write(lock->lock_fd, &term, 1) != 1
 789                 || close(lock->lock_fd) < 0) {
 790                 error("Couldn't write %s", lock->lk->filename);
 791                 unlock_ref(lock);
 792                 return -1;
 793         }
 794         invalidate_cached_refs();
 795         if (log_ref_write(lock, sha1, logmsg) < 0) {
 796                 unlock_ref(lock);
 797                 return -1;
 798         }
 799         if (commit_lock_file(lock->lk)) {
 800                 error("Couldn't set %s", lock->ref_name);
 801                 unlock_ref(lock);
 802                 return -1;
 803         }
 804         lock->lock_fd = -1;
 805         unlock_ref(lock);
 806         return 0;
 807 }
 808
 809 int read_ref_at(const char *ref, unsigned long at_time, unsigned char *sha1)
 810 {
 811         const char *logfile, *logdata, *logend, *rec, *lastgt, *lastrec;
 812         char *tz_c;
 813         int logfd, tz;
 814         struct stat st;
 815         unsigned long date;
 816         unsigned char logged_sha1[20];
 817
 818         logfile = git_path("logs/%s", ref);
 819         logfd = open(logfile, O_RDONLY, 0);
 820         if (logfd < 0)
 821                 die("Unable to read log %s: %s", logfile, strerror(errno));
 822         fstat(logfd, &st);
 823         if (!st.st_size)
 824                 die("Log %s is empty.", logfile);
 825         logdata = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, logfd, 0);
 826         close(logfd);
 827
 828         lastrec = NULL;
 829         rec = logend = logdata + st.st_size;
 830         while (logdata < rec) {
 831                 if (logdata < rec && *(rec-1) == '\n')
 832                         rec--;
 833                 lastgt = NULL;
 834                 while (logdata < rec && *(rec-1) != '\n') {
 835                         rec--;
 836                         if (*rec == '>')
 837                                 lastgt = rec;
 838                 }
 839                 if (!lastgt)
 840                         die("Log %s is corrupt.", logfile);
 841                 date = strtoul(lastgt + 1, &tz_c, 10);
 842                 if (date <= at_time) {
 843                         if (lastrec) {
 844                                 if (get_sha1_hex(lastrec, logged_sha1))
 845                                         die("Log %s is corrupt.", logfile);
 846                                 if (get_sha1_hex(rec + 41, sha1))
 847                                         die("Log %s is corrupt.", logfile);
 848                                 if (hashcmp(logged_sha1, sha1)) {
 849                                         tz = strtoul(tz_c, NULL, 10);
 850                                         fprintf(stderr,
 851                                                 "warning: Log %s has gap after %s.\n",
 852                                                 logfile, show_rfc2822_date(date, tz));
 853                                 }
 854                         }
 855                         else if (date == at_time) {
 856                                 if (get_sha1_hex(rec + 41, sha1))
 857                                         die("Log %s is corrupt.", logfile);
 858                         }
 859                         else {
 860                                 if (get_sha1_hex(rec + 41, logged_sha1))
 861                                         die("Log %s is corrupt.", logfile);
 862                                 if (hashcmp(logged_sha1, sha1)) {
 863                                         tz = strtoul(tz_c, NULL, 10);
 864                                         fprintf(stderr,
 865                                                 "warning: Log %s unexpectedly ended on %s.\n",
 866                                                 logfile, show_rfc2822_date(date, tz));
 867                                 }
 868                         }
 869                         munmap((void*)logdata, st.st_size);
 870                         return 0;
 871                 }
 872                 lastrec = rec;
 873         }
 874
 875         rec = logdata;
 876         while (rec < logend && *rec != '>' && *rec != '\n')
 877                 rec++;
 878         if (rec == logend || *rec == '\n')
 879                 die("Log %s is corrupt.", logfile);
 880         date = strtoul(rec + 1, &tz_c, 10);
 881         tz = strtoul(tz_c, NULL, 10);
 882         if (get_sha1_hex(logdata, sha1))
 883                 die("Log %s is corrupt.", logfile);
 884         munmap((void*)logdata, st.st_size);
 885         fprintf(stderr, "warning: Log %s only goes back to %s.\n",
 886                 logfile, show_rfc2822_date(date, tz));
 887         return 0;
 888 }