refs.con commit Merge branch 'sb/fetch' into jc/refs-and-fetch (12f9b8a)
   1#include "refs.h"
   2#include "cache.h"
   3
   4#include <errno.h>
   5
   6struct 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
  13static 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
  40static 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 */
  73struct cached_refs {
  74        char did_loose;
  75        char did_packed;
  76        struct ref_list *loose;
  77        struct ref_list *packed;
  78} cached_refs;
  79
  80static 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
  89static 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
 101static 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
 125static 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
 170static 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
 182const 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                /*
 238                 * Anything else, just open it and try to use it as
 239                 * a ref
 240                 */
 241                fd = open(path, O_RDONLY);
 242                if (fd < 0)
 243                        return NULL;
 244                len = read(fd, buffer, sizeof(buffer)-1);
 245                close(fd);
 246
 247                /*
 248                 * Is it a symbolic ref?
 249                 */
 250                if (len < 4 || memcmp("ref:", buffer, 4))
 251                        break;
 252                buf = buffer + 4;
 253                len -= 4;
 254                while (len && isspace(*buf))
 255                        buf++, len--;
 256                while (len && isspace(buf[len-1]))
 257                        len--;
 258                buf[len] = 0;
 259                memcpy(ref_buffer, buf, len + 1);
 260                ref = ref_buffer;
 261                if (flag)
 262                        *flag |= REF_ISSYMREF;
 263        }
 264        if (len < 40 || get_sha1_hex(buffer, sha1))
 265                return NULL;
 266        return ref;
 267}
 268
 269int create_symref(const char *ref_target, const char *refs_heads_master)
 270{
 271        const char *lockpath;
 272        char ref[1000];
 273        int fd, len, written;
 274        const char *git_HEAD = git_path("%s", ref_target);
 275
 276#ifndef NO_SYMLINK_HEAD
 277        if (prefer_symlink_refs) {
 278                unlink(git_HEAD);
 279                if (!symlink(refs_heads_master, git_HEAD))
 280                        return 0;
 281                fprintf(stderr, "no symlink - falling back to symbolic ref\n");
 282        }
 283#endif
 284
 285        len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
 286        if (sizeof(ref) <= len) {
 287                error("refname too long: %s", refs_heads_master);
 288                return -1;
 289        }
 290        lockpath = mkpath("%s.lock", git_HEAD);
 291        fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666); 
 292        written = write(fd, ref, len);
 293        close(fd);
 294        if (written != len) {
 295                unlink(lockpath);
 296                error("Unable to write to %s", lockpath);
 297                return -2;
 298        }
 299        if (rename(lockpath, git_HEAD) < 0) {
 300                unlink(lockpath);
 301                error("Unable to create %s", git_HEAD);
 302                return -3;
 303        }
 304        if (adjust_shared_perm(git_HEAD)) {
 305                unlink(lockpath);
 306                error("Unable to fix permissions on %s", lockpath);
 307                return -4;
 308        }
 309        return 0;
 310}
 311
 312int read_ref(const char *ref, unsigned char *sha1)
 313{
 314        if (resolve_ref(ref, sha1, 1, NULL))
 315                return 0;
 316        return -1;
 317}
 318
 319static int do_for_each_ref(const char *base, each_ref_fn fn, int trim,
 320                           void *cb_data)
 321{
 322        int retval;
 323        struct ref_list *packed = get_packed_refs();
 324        struct ref_list *loose = get_loose_refs();
 325
 326        while (packed && loose) {
 327                struct ref_list *entry;
 328                int cmp = strcmp(packed->name, loose->name);
 329                if (!cmp) {
 330                        packed = packed->next;
 331                        continue;
 332                }
 333                if (cmp > 0) {
 334                        entry = loose;
 335                        loose = loose->next;
 336                } else {
 337                        entry = packed;
 338                        packed = packed->next;
 339                }
 340                if (strncmp(base, entry->name, trim))
 341                        continue;
 342                if (is_null_sha1(entry->sha1))
 343                        continue;
 344                if (!has_sha1_file(entry->sha1)) {
 345                        error("%s does not point to a valid object!", entry->name);
 346                        continue;
 347                }
 348                retval = fn(entry->name + trim, entry->sha1,
 349                            entry->flag, cb_data);
 350                if (retval)
 351                        return retval;
 352        }
 353
 354        packed = packed ? packed : loose;
 355        while (packed) {
 356                if (!strncmp(base, packed->name, trim)) {
 357                        retval = fn(packed->name + trim, packed->sha1,
 358                                    packed->flag, cb_data);
 359                        if (retval)
 360                                return retval;
 361                }
 362                packed = packed->next;
 363        }
 364        return 0;
 365}
 366
 367int head_ref(each_ref_fn fn, void *cb_data)
 368{
 369        unsigned char sha1[20];
 370        int flag;
 371
 372        if (resolve_ref("HEAD", sha1, 1, &flag))
 373                return fn("HEAD", sha1, flag, cb_data);
 374        return 0;
 375}
 376
 377int for_each_ref(each_ref_fn fn, void *cb_data)
 378{
 379        return do_for_each_ref("refs/", fn, 0, cb_data);
 380}
 381
 382int for_each_tag_ref(each_ref_fn fn, void *cb_data)
 383{
 384        return do_for_each_ref("refs/tags/", fn, 10, cb_data);
 385}
 386
 387int for_each_branch_ref(each_ref_fn fn, void *cb_data)
 388{
 389        return do_for_each_ref("refs/heads/", fn, 11, cb_data);
 390}
 391
 392int for_each_remote_ref(each_ref_fn fn, void *cb_data)
 393{
 394        return do_for_each_ref("refs/remotes/", fn, 13, cb_data);
 395}
 396
 397/* NEEDSWORK: This is only used by ssh-upload and it should go; the
 398 * caller should do resolve_ref or read_ref like everybody else.  Or
 399 * maybe everybody else should use get_ref_sha1() instead of doing
 400 * read_ref().
 401 */
 402int get_ref_sha1(const char *ref, unsigned char *sha1)
 403{
 404        if (check_ref_format(ref))
 405                return -1;
 406        return read_ref(mkpath("refs/%s", ref), sha1);
 407}
 408
 409/*
 410 * Make sure "ref" is something reasonable to have under ".git/refs/";
 411 * We do not like it if:
 412 *
 413 * - any path component of it begins with ".", or
 414 * - it has double dots "..", or
 415 * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 416 * - it ends with a "/".
 417 */
 418
 419static inline int bad_ref_char(int ch)
 420{
 421        return (((unsigned) ch) <= ' ' ||
 422                ch == '~' || ch == '^' || ch == ':' ||
 423                /* 2.13 Pattern Matching Notation */
 424                ch == '?' || ch == '*' || ch == '[');
 425}
 426
 427int check_ref_format(const char *ref)
 428{
 429        int ch, level;
 430        const char *cp = ref;
 431
 432        level = 0;
 433        while (1) {
 434                while ((ch = *cp++) == '/')
 435                        ; /* tolerate duplicated slashes */
 436                if (!ch)
 437                        return -1; /* should not end with slashes */
 438
 439                /* we are at the beginning of the path component */
 440                if (ch == '.' || bad_ref_char(ch))
 441                        return -1;
 442
 443                /* scan the rest of the path component */
 444                while ((ch = *cp++) != 0) {
 445                        if (bad_ref_char(ch))
 446                                return -1;
 447                        if (ch == '/')
 448                                break;
 449                        if (ch == '.' && *cp == '.')
 450                                return -1;
 451                }
 452                level++;
 453                if (!ch) {
 454                        if (level < 2)
 455                                return -1; /* at least of form "heads/blah" */
 456                        return 0;
 457                }
 458        }
 459}
 460
 461static struct ref_lock *verify_lock(struct ref_lock *lock,
 462        const unsigned char *old_sha1, int mustexist)
 463{
 464        if (!resolve_ref(lock->ref_name, lock->old_sha1, mustexist, NULL)) {
 465                error("Can't verify ref %s", lock->ref_name);
 466                unlock_ref(lock);
 467                return NULL;
 468        }
 469        if (hashcmp(lock->old_sha1, old_sha1)) {
 470                error("Ref %s is at %s but expected %s", lock->ref_name,
 471                        sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
 472                unlock_ref(lock);
 473                return NULL;
 474        }
 475        return lock;
 476}
 477
 478static int remove_empty_dir_recursive(char *path, int len)
 479{
 480        DIR *dir = opendir(path);
 481        struct dirent *e;
 482        int ret = 0;
 483
 484        if (!dir)
 485                return -1;
 486        if (path[len-1] != '/')
 487                path[len++] = '/';
 488        while ((e = readdir(dir)) != NULL) {
 489                struct stat st;
 490                int namlen;
 491                if ((e->d_name[0] == '.') &&
 492                    ((e->d_name[1] == 0) ||
 493                     ((e->d_name[1] == '.') && e->d_name[2] == 0)))
 494                        continue; /* "." and ".." */
 495
 496                namlen = strlen(e->d_name);
 497                if ((len + namlen < PATH_MAX) &&
 498                    strcpy(path + len, e->d_name) &&
 499                    !lstat(path, &st) &&
 500                    S_ISDIR(st.st_mode) &&
 501                    remove_empty_dir_recursive(path, len + namlen))
 502                        continue; /* happy */
 503
 504                /* path too long, stat fails, or non-directory still exists */
 505                ret = -1;
 506                break;
 507        }
 508        closedir(dir);
 509        if (!ret) {
 510                path[len] = 0;
 511                ret = rmdir(path);
 512        }
 513        return ret;
 514}
 515
 516static int remove_empty_directories(char *file)
 517{
 518        /* we want to create a file but there is a directory there;
 519         * if that is an empty directory (or a directory that contains
 520         * only empty directories), remove them.
 521         */
 522        char path[PATH_MAX];
 523        int len = strlen(file);
 524
 525        if (len >= PATH_MAX) /* path too long ;-) */
 526                return -1;
 527        strcpy(path, file);
 528        return remove_empty_dir_recursive(path, len);
 529}
 530
 531static struct ref_lock *lock_ref_sha1_basic(const char *ref, const unsigned char *old_sha1, int *flag)
 532{
 533        char *ref_file;
 534        const char *orig_ref = ref;
 535        struct ref_lock *lock;
 536        struct stat st;
 537        int last_errno = 0;
 538        int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
 539
 540        lock = xcalloc(1, sizeof(struct ref_lock));
 541        lock->lock_fd = -1;
 542
 543        ref = resolve_ref(ref, lock->old_sha1, mustexist, flag);
 544        if (!ref && errno == EISDIR) {
 545                /* we are trying to lock foo but we used to
 546                 * have foo/bar which now does not exist;
 547                 * it is normal for the empty directory 'foo'
 548                 * to remain.
 549                 */
 550                ref_file = git_path("%s", orig_ref);
 551                if (remove_empty_directories(ref_file)) {
 552                        last_errno = errno;
 553                        error("there are still refs under '%s'", orig_ref);
 554                        goto error_return;
 555                }
 556                ref = resolve_ref(orig_ref, lock->old_sha1, mustexist, flag);
 557        }
 558        if (!ref) {
 559                last_errno = errno;
 560                error("unable to resolve reference %s: %s",
 561                        orig_ref, strerror(errno));
 562                goto error_return;
 563        }
 564        if (is_null_sha1(lock->old_sha1)) {
 565                /* The ref did not exist and we are creating it.
 566                 * Make sure there is no existing ref that is packed
 567                 * whose name begins with our refname, nor a ref whose
 568                 * name is a proper prefix of our refname.
 569                 */
 570                int namlen = strlen(ref); /* e.g. 'foo/bar' */
 571                struct ref_list *list = get_packed_refs();
 572                while (list) {
 573                        /* list->name could be 'foo' or 'foo/bar/baz' */
 574                        int len = strlen(list->name);
 575                        int cmplen = (namlen < len) ? namlen : len;
 576                        const char *lead = (namlen < len) ? list->name : ref;
 577
 578                        if (!strncmp(ref, list->name, cmplen) &&
 579                            lead[cmplen] == '/') {
 580                                error("'%s' exists; cannot create '%s'",
 581                                      list->name, ref);
 582                                goto error_return;
 583                        }
 584                        list = list->next;
 585                }
 586        }
 587
 588        lock->lk = xcalloc(1, sizeof(struct lock_file));
 589
 590        lock->ref_name = xstrdup(ref);
 591        lock->log_file = xstrdup(git_path("logs/%s", ref));
 592        ref_file = git_path("%s", ref);
 593        lock->force_write = lstat(ref_file, &st) && errno == ENOENT;
 594
 595        if (safe_create_leading_directories(ref_file)) {
 596                last_errno = errno;
 597                error("unable to create directory for %s", ref_file);
 598                goto error_return;
 599        }
 600        lock->lock_fd = hold_lock_file_for_update(lock->lk, ref_file, 1);
 601
 602        return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
 603
 604 error_return:
 605        unlock_ref(lock);
 606        errno = last_errno;
 607        return NULL;
 608}
 609
 610struct ref_lock *lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 611{
 612        char refpath[PATH_MAX];
 613        if (check_ref_format(ref))
 614                return NULL;
 615        strcpy(refpath, mkpath("refs/%s", ref));
 616        return lock_ref_sha1_basic(refpath, old_sha1, NULL);
 617}
 618
 619struct ref_lock *lock_any_ref_for_update(const char *ref, const unsigned char *old_sha1)
 620{
 621        return lock_ref_sha1_basic(ref, old_sha1, NULL);
 622}
 623
 624static int repack_without_ref(const char *refname)
 625{
 626        struct ref_list *list, *packed_ref_list;
 627        int fd;
 628        int found = 0;
 629        struct lock_file packlock;
 630
 631        packed_ref_list = get_packed_refs();
 632        for (list = packed_ref_list; list; list = list->next) {
 633                if (!strcmp(refname, list->name)) {
 634                        found = 1;
 635                        break;
 636                }
 637        }
 638        if (!found)
 639                return 0;
 640        memset(&packlock, 0, sizeof(packlock));
 641        fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"), 0);
 642        if (fd < 0)
 643                return error("cannot delete '%s' from packed refs", refname);
 644
 645        for (list = packed_ref_list; list; list = list->next) {
 646                char line[PATH_MAX + 100];
 647                int len;
 648
 649                if (!strcmp(refname, list->name))
 650                        continue;
 651                len = snprintf(line, sizeof(line), "%s %s\n",
 652                               sha1_to_hex(list->sha1), list->name);
 653                /* this should not happen but just being defensive */
 654                if (len > sizeof(line))
 655                        die("too long a refname '%s'", list->name);
 656                write_or_die(fd, line, len);
 657        }
 658        return commit_lock_file(&packlock);
 659}
 660
 661int delete_ref(const char *refname, unsigned char *sha1)
 662{
 663        struct ref_lock *lock;
 664        int err, i, ret = 0, flag = 0;
 665
 666        lock = lock_ref_sha1_basic(refname, sha1, &flag);
 667        if (!lock)
 668                return 1;
 669        if (!(flag & REF_ISPACKED)) {
 670                /* loose */
 671                i = strlen(lock->lk->filename) - 5; /* .lock */
 672                lock->lk->filename[i] = 0;
 673                err = unlink(lock->lk->filename);
 674                if (err) {
 675                        ret = 1;
 676                        error("unlink(%s) failed: %s",
 677                              lock->lk->filename, strerror(errno));
 678                }
 679                lock->lk->filename[i] = '.';
 680        }
 681        /* removing the loose one could have resurrected an earlier
 682         * packed one.  Also, if it was not loose we need to repack
 683         * without it.
 684         */
 685        ret |= repack_without_ref(refname);
 686
 687        err = unlink(lock->log_file);
 688        if (err && errno != ENOENT)
 689                fprintf(stderr, "warning: unlink(%s) failed: %s",
 690                        lock->log_file, strerror(errno));
 691        invalidate_cached_refs();
 692        unlock_ref(lock);
 693        return ret;
 694}
 695
 696void unlock_ref(struct ref_lock *lock)
 697{
 698        if (lock->lock_fd >= 0) {
 699                close(lock->lock_fd);
 700                /* Do not free lock->lk -- atexit() still looks at them */
 701                if (lock->lk)
 702                        rollback_lock_file(lock->lk);
 703        }
 704        free(lock->ref_name);
 705        free(lock->log_file);
 706        free(lock);
 707}
 708
 709static int log_ref_write(struct ref_lock *lock,
 710        const unsigned char *sha1, const char *msg)
 711{
 712        int logfd, written, oflags = O_APPEND | O_WRONLY;
 713        unsigned maxlen, len;
 714        char *logrec;
 715        const char *committer;
 716
 717        if (log_all_ref_updates) {
 718                if (safe_create_leading_directories(lock->log_file) < 0)
 719                        return error("unable to create directory for %s",
 720                                lock->log_file);
 721                oflags |= O_CREAT;
 722        }
 723
 724        logfd = open(lock->log_file, oflags, 0666);
 725        if (logfd < 0) {
 726                if (!log_all_ref_updates && errno == ENOENT)
 727                        return 0;
 728                return error("Unable to append to %s: %s",
 729                        lock->log_file, strerror(errno));
 730        }
 731
 732        committer = git_committer_info(1);
 733        if (msg) {
 734                maxlen = strlen(committer) + strlen(msg) + 2*40 + 5;
 735                logrec = xmalloc(maxlen);
 736                len = snprintf(logrec, maxlen, "%s %s %s\t%s\n",
 737                        sha1_to_hex(lock->old_sha1),
 738                        sha1_to_hex(sha1),
 739                        committer,
 740                        msg);
 741        }
 742        else {
 743                maxlen = strlen(committer) + 2*40 + 4;
 744                logrec = xmalloc(maxlen);
 745                len = snprintf(logrec, maxlen, "%s %s %s\n",
 746                        sha1_to_hex(lock->old_sha1),
 747                        sha1_to_hex(sha1),
 748                        committer);
 749        }
 750        written = len <= maxlen ? write(logfd, logrec, len) : -1;
 751        free(logrec);
 752        close(logfd);
 753        if (written != len)
 754                return error("Unable to append to %s", lock->log_file);
 755        return 0;
 756}
 757
 758int write_ref_sha1(struct ref_lock *lock,
 759        const unsigned char *sha1, const char *logmsg)
 760{
 761        static char term = '\n';
 762
 763        if (!lock)
 764                return -1;
 765        if (!lock->force_write && !hashcmp(lock->old_sha1, sha1)) {
 766                unlock_ref(lock);
 767                return 0;
 768        }
 769        if (write(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
 770            write(lock->lock_fd, &term, 1) != 1
 771                || close(lock->lock_fd) < 0) {
 772                error("Couldn't write %s", lock->lk->filename);
 773                unlock_ref(lock);
 774                return -1;
 775        }
 776        invalidate_cached_refs();
 777        if (log_ref_write(lock, sha1, logmsg) < 0) {
 778                unlock_ref(lock);
 779                return -1;
 780        }
 781        if (commit_lock_file(lock->lk)) {
 782                error("Couldn't set %s", lock->ref_name);
 783                unlock_ref(lock);
 784                return -1;
 785        }
 786        lock->lock_fd = -1;
 787        unlock_ref(lock);
 788        return 0;
 789}
 790
 791int read_ref_at(const char *ref, unsigned long at_time, unsigned char *sha1)
 792{
 793        const char *logfile, *logdata, *logend, *rec, *lastgt, *lastrec;
 794        char *tz_c;
 795        int logfd, tz;
 796        struct stat st;
 797        unsigned long date;
 798        unsigned char logged_sha1[20];
 799
 800        logfile = git_path("logs/%s", ref);
 801        logfd = open(logfile, O_RDONLY, 0);
 802        if (logfd < 0)
 803                die("Unable to read log %s: %s", logfile, strerror(errno));
 804        fstat(logfd, &st);
 805        if (!st.st_size)
 806                die("Log %s is empty.", logfile);
 807        logdata = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, logfd, 0);
 808        close(logfd);
 809
 810        lastrec = NULL;
 811        rec = logend = logdata + st.st_size;
 812        while (logdata < rec) {
 813                if (logdata < rec && *(rec-1) == '\n')
 814                        rec--;
 815                lastgt = NULL;
 816                while (logdata < rec && *(rec-1) != '\n') {
 817                        rec--;
 818                        if (*rec == '>')
 819                                lastgt = rec;
 820                }
 821                if (!lastgt)
 822                        die("Log %s is corrupt.", logfile);
 823                date = strtoul(lastgt + 1, &tz_c, 10);
 824                if (date <= at_time) {
 825                        if (lastrec) {
 826                                if (get_sha1_hex(lastrec, logged_sha1))
 827                                        die("Log %s is corrupt.", logfile);
 828                                if (get_sha1_hex(rec + 41, sha1))
 829                                        die("Log %s is corrupt.", logfile);
 830                                if (hashcmp(logged_sha1, sha1)) {
 831                                        tz = strtoul(tz_c, NULL, 10);
 832                                        fprintf(stderr,
 833                                                "warning: Log %s has gap after %s.\n",
 834                                                logfile, show_rfc2822_date(date, tz));
 835                                }
 836                        }
 837                        else if (date == at_time) {
 838                                if (get_sha1_hex(rec + 41, sha1))
 839                                        die("Log %s is corrupt.", logfile);
 840                        }
 841                        else {
 842                                if (get_sha1_hex(rec + 41, logged_sha1))
 843                                        die("Log %s is corrupt.", logfile);
 844                                if (hashcmp(logged_sha1, sha1)) {
 845                                        tz = strtoul(tz_c, NULL, 10);
 846                                        fprintf(stderr,
 847                                                "warning: Log %s unexpectedly ended on %s.\n",
 848                                                logfile, show_rfc2822_date(date, tz));
 849                                }
 850                        }
 851                        munmap((void*)logdata, st.st_size);
 852                        return 0;
 853                }
 854                lastrec = rec;
 855        }
 856
 857        rec = logdata;
 858        while (rec < logend && *rec != '>' && *rec != '\n')
 859                rec++;
 860        if (rec == logend || *rec == '\n')
 861                die("Log %s is corrupt.", logfile);
 862        date = strtoul(rec + 1, &tz_c, 10);
 863        tz = strtoul(tz_c, NULL, 10);
 864        if (get_sha1_hex(logdata, sha1))
 865                die("Log %s is corrupt.", logfile);
 866        munmap((void*)logdata, st.st_size);
 867        fprintf(stderr, "warning: Log %s only goes back to %s.\n",
 868                logfile, show_rfc2822_date(date, tz));
 869        return 0;
 870}