197579205bf8dcc2dc2c1950ef27c7385a50697a
   1#include "cache.h"
   2#include "refs.h"
   3#include "object.h"
   4#include "tag.h"
   5#include "dir.h"
   6
   7/* ISSYMREF=0x01, ISPACKED=0x02 and ISBROKEN=0x04 are public interfaces */
   8#define REF_KNOWS_PEELED 0x10
   9
  10struct ref_entry {
  11        unsigned char flag; /* ISSYMREF? ISPACKED? */
  12        unsigned char sha1[20];
  13        unsigned char peeled[20];
  14        /* The full name of the reference (e.g., "refs/heads/master"): */
  15        char name[FLEX_ARRAY];
  16};
  17
  18struct ref_array {
  19        int nr, alloc;
  20        struct ref_entry **refs;
  21};
  22
  23/*
  24 * Parse one line from a packed-refs file.  Write the SHA1 to sha1.
  25 * Return a pointer to the refname within the line (null-terminated),
  26 * or NULL if there was a problem.
  27 */
  28static const char *parse_ref_line(char *line, unsigned char *sha1)
  29{
  30        /*
  31         * 42: the answer to everything.
  32         *
  33         * In this case, it happens to be the answer to
  34         *  40 (length of sha1 hex representation)
  35         *  +1 (space in between hex and name)
  36         *  +1 (newline at the end of the line)
  37         */
  38        int len = strlen(line) - 42;
  39
  40        if (len <= 0)
  41                return NULL;
  42        if (get_sha1_hex(line, sha1) < 0)
  43                return NULL;
  44        if (!isspace(line[40]))
  45                return NULL;
  46        line += 41;
  47        if (isspace(*line))
  48                return NULL;
  49        if (line[len] != '\n')
  50                return NULL;
  51        line[len] = 0;
  52
  53        return line;
  54}
  55
  56static void add_ref(const char *refname, const unsigned char *sha1,
  57                    int flag, int check_name, struct ref_array *refs,
  58                    struct ref_entry **new_entry)
  59{
  60        int len;
  61        struct ref_entry *entry;
  62
  63        /* Allocate it and add it in.. */
  64        len = strlen(refname) + 1;
  65        entry = xmalloc(sizeof(struct ref_entry) + len);
  66        hashcpy(entry->sha1, sha1);
  67        hashclr(entry->peeled);
  68        if (check_name &&
  69            check_refname_format(refname, REFNAME_ALLOW_ONELEVEL|REFNAME_DOT_COMPONENT))
  70                die("Reference has invalid format: '%s'", refname);
  71        memcpy(entry->name, refname, len);
  72        entry->flag = flag;
  73        if (new_entry)
  74                *new_entry = entry;
  75        ALLOC_GROW(refs->refs, refs->nr + 1, refs->alloc);
  76        refs->refs[refs->nr++] = entry;
  77}
  78
  79static int ref_entry_cmp(const void *a, const void *b)
  80{
  81        struct ref_entry *one = *(struct ref_entry **)a;
  82        struct ref_entry *two = *(struct ref_entry **)b;
  83        return strcmp(one->name, two->name);
  84}
  85
  86static void sort_ref_array(struct ref_array *array)
  87{
  88        int i = 0, j = 1;
  89
  90        /* Nothing to sort unless there are at least two entries */
  91        if (array->nr < 2)
  92                return;
  93
  94        qsort(array->refs, array->nr, sizeof(*array->refs), ref_entry_cmp);
  95
  96        /* Remove any duplicates from the ref_array */
  97        for (; j < array->nr; j++) {
  98                struct ref_entry *a = array->refs[i];
  99                struct ref_entry *b = array->refs[j];
 100                if (!strcmp(a->name, b->name)) {
 101                        if (hashcmp(a->sha1, b->sha1))
 102                                die("Duplicated ref, and SHA1s don't match: %s",
 103                                    a->name);
 104                        warning("Duplicated ref: %s", a->name);
 105                        free(b);
 106                        continue;
 107                }
 108                i++;
 109                array->refs[i] = array->refs[j];
 110        }
 111        array->nr = i + 1;
 112}
 113
 114static struct ref_entry *search_ref_array(struct ref_array *array, const char *refname)
 115{
 116        struct ref_entry *e, **r;
 117        int len;
 118
 119        if (refname == NULL)
 120                return NULL;
 121
 122        if (!array->nr)
 123                return NULL;
 124
 125        len = strlen(refname) + 1;
 126        e = xmalloc(sizeof(struct ref_entry) + len);
 127        memcpy(e->name, refname, len);
 128
 129        r = bsearch(&e, array->refs, array->nr, sizeof(*array->refs), ref_entry_cmp);
 130
 131        free(e);
 132
 133        if (r == NULL)
 134                return NULL;
 135
 136        return *r;
 137}
 138
 139/*
 140 * Future: need to be in "struct repository"
 141 * when doing a full libification.
 142 */
 143static struct ref_cache {
 144        struct ref_cache *next;
 145        char did_loose;
 146        char did_packed;
 147        struct ref_array loose;
 148        struct ref_array packed;
 149        /* The submodule name, or "" for the main repo. */
 150        char name[FLEX_ARRAY];
 151} *ref_cache;
 152
 153static struct ref_entry *current_ref;
 154
 155static struct ref_array extra_refs;
 156
 157static void clear_ref_array(struct ref_array *array)
 158{
 159        int i;
 160        for (i = 0; i < array->nr; i++)
 161                free(array->refs[i]);
 162        free(array->refs);
 163        array->nr = array->alloc = 0;
 164        array->refs = NULL;
 165}
 166
 167static void clear_packed_ref_cache(struct ref_cache *refs)
 168{
 169        if (refs->did_packed)
 170                clear_ref_array(&refs->packed);
 171        refs->did_packed = 0;
 172}
 173
 174static void clear_loose_ref_cache(struct ref_cache *refs)
 175{
 176        if (refs->did_loose)
 177                clear_ref_array(&refs->loose);
 178        refs->did_loose = 0;
 179}
 180
 181static struct ref_cache *create_ref_cache(const char *submodule)
 182{
 183        int len;
 184        struct ref_cache *refs;
 185        if (!submodule)
 186                submodule = "";
 187        len = strlen(submodule) + 1;
 188        refs = xcalloc(1, sizeof(struct ref_cache) + len);
 189        memcpy(refs->name, submodule, len);
 190        return refs;
 191}
 192
 193/*
 194 * Return a pointer to a ref_cache for the specified submodule. For
 195 * the main repository, use submodule==NULL. The returned structure
 196 * will be allocated and initialized but not necessarily populated; it
 197 * should not be freed.
 198 */
 199static struct ref_cache *get_ref_cache(const char *submodule)
 200{
 201        struct ref_cache *refs = ref_cache;
 202        if (!submodule)
 203                submodule = "";
 204        while (refs) {
 205                if (!strcmp(submodule, refs->name))
 206                        return refs;
 207                refs = refs->next;
 208        }
 209
 210        refs = create_ref_cache(submodule);
 211        refs->next = ref_cache;
 212        ref_cache = refs;
 213        return refs;
 214}
 215
 216void invalidate_ref_cache(const char *submodule)
 217{
 218        struct ref_cache *refs = get_ref_cache(submodule);
 219        clear_packed_ref_cache(refs);
 220        clear_loose_ref_cache(refs);
 221}
 222
 223static void read_packed_refs(FILE *f, struct ref_array *array)
 224{
 225        struct ref_entry *last = NULL;
 226        char refline[PATH_MAX];
 227        int flag = REF_ISPACKED;
 228
 229        while (fgets(refline, sizeof(refline), f)) {
 230                unsigned char sha1[20];
 231                const char *refname;
 232                static const char header[] = "# pack-refs with:";
 233
 234                if (!strncmp(refline, header, sizeof(header)-1)) {
 235                        const char *traits = refline + sizeof(header) - 1;
 236                        if (strstr(traits, " peeled "))
 237                                flag |= REF_KNOWS_PEELED;
 238                        /* perhaps other traits later as well */
 239                        continue;
 240                }
 241
 242                refname = parse_ref_line(refline, sha1);
 243                if (refname) {
 244                        add_ref(refname, sha1, flag, 1, array, &last);
 245                        continue;
 246                }
 247                if (last &&
 248                    refline[0] == '^' &&
 249                    strlen(refline) == 42 &&
 250                    refline[41] == '\n' &&
 251                    !get_sha1_hex(refline + 1, sha1))
 252                        hashcpy(last->peeled, sha1);
 253        }
 254        sort_ref_array(array);
 255}
 256
 257void add_extra_ref(const char *refname, const unsigned char *sha1, int flag)
 258{
 259        add_ref(refname, sha1, flag, 0, &extra_refs, NULL);
 260}
 261
 262void clear_extra_refs(void)
 263{
 264        clear_ref_array(&extra_refs);
 265}
 266
 267static struct ref_array *get_packed_refs(const char *submodule)
 268{
 269        struct ref_cache *refs = get_ref_cache(submodule);
 270
 271        if (!refs->did_packed) {
 272                const char *packed_refs_file;
 273                FILE *f;
 274
 275                if (submodule)
 276                        packed_refs_file = git_path_submodule(submodule, "packed-refs");
 277                else
 278                        packed_refs_file = git_path("packed-refs");
 279                f = fopen(packed_refs_file, "r");
 280                if (f) {
 281                        read_packed_refs(f, &refs->packed);
 282                        fclose(f);
 283                }
 284                refs->did_packed = 1;
 285        }
 286        return &refs->packed;
 287}
 288
 289static void get_ref_dir(const char *submodule, const char *base,
 290                        struct ref_array *array)
 291{
 292        DIR *dir;
 293        const char *path;
 294
 295        if (submodule)
 296                path = git_path_submodule(submodule, "%s", base);
 297        else
 298                path = git_path("%s", base);
 299
 300
 301        dir = opendir(path);
 302
 303        if (dir) {
 304                struct dirent *de;
 305                int baselen = strlen(base);
 306                char *refname = xmalloc(baselen + 257);
 307
 308                memcpy(refname, base, baselen);
 309                if (baselen && base[baselen-1] != '/')
 310                        refname[baselen++] = '/';
 311
 312                while ((de = readdir(dir)) != NULL) {
 313                        unsigned char sha1[20];
 314                        struct stat st;
 315                        int flag;
 316                        int namelen;
 317                        const char *refdir;
 318
 319                        if (de->d_name[0] == '.')
 320                                continue;
 321                        namelen = strlen(de->d_name);
 322                        if (namelen > 255)
 323                                continue;
 324                        if (has_extension(de->d_name, ".lock"))
 325                                continue;
 326                        memcpy(refname + baselen, de->d_name, namelen+1);
 327                        refdir = submodule
 328                                ? git_path_submodule(submodule, "%s", refname)
 329                                : git_path("%s", refname);
 330                        if (stat(refdir, &st) < 0)
 331                                continue;
 332                        if (S_ISDIR(st.st_mode)) {
 333                                get_ref_dir(submodule, refname, array);
 334                                continue;
 335                        }
 336                        if (submodule) {
 337                                hashclr(sha1);
 338                                flag = 0;
 339                                if (resolve_gitlink_ref(submodule, refname, sha1) < 0) {
 340                                        hashclr(sha1);
 341                                        flag |= REF_ISBROKEN;
 342                                }
 343                        } else if (read_ref_full(refname, sha1, 1, &flag)) {
 344                                hashclr(sha1);
 345                                flag |= REF_ISBROKEN;
 346                        }
 347                        add_ref(refname, sha1, flag, 1, array, NULL);
 348                }
 349                free(refname);
 350                closedir(dir);
 351        }
 352}
 353
 354struct warn_if_dangling_data {
 355        FILE *fp;
 356        const char *refname;
 357        const char *msg_fmt;
 358};
 359
 360static int warn_if_dangling_symref(const char *refname, const unsigned char *sha1,
 361                                   int flags, void *cb_data)
 362{
 363        struct warn_if_dangling_data *d = cb_data;
 364        const char *resolves_to;
 365        unsigned char junk[20];
 366
 367        if (!(flags & REF_ISSYMREF))
 368                return 0;
 369
 370        resolves_to = resolve_ref(refname, junk, 0, NULL);
 371        if (!resolves_to || strcmp(resolves_to, d->refname))
 372                return 0;
 373
 374        fprintf(d->fp, d->msg_fmt, refname);
 375        return 0;
 376}
 377
 378void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname)
 379{
 380        struct warn_if_dangling_data data;
 381
 382        data.fp = fp;
 383        data.refname = refname;
 384        data.msg_fmt = msg_fmt;
 385        for_each_rawref(warn_if_dangling_symref, &data);
 386}
 387
 388static struct ref_array *get_loose_refs(const char *submodule)
 389{
 390        struct ref_cache *refs = get_ref_cache(submodule);
 391
 392        if (!refs->did_loose) {
 393                get_ref_dir(submodule, "refs", &refs->loose);
 394                sort_ref_array(&refs->loose);
 395                refs->did_loose = 1;
 396        }
 397        return &refs->loose;
 398}
 399
 400/* We allow "recursive" symbolic refs. Only within reason, though */
 401#define MAXDEPTH 5
 402#define MAXREFLEN (1024)
 403
 404/*
 405 * Called by resolve_gitlink_ref_recursive() after it failed to read
 406 * from "name", which is "module/.git/<refname>". Find <refname> in
 407 * the packed-refs file for the submodule.
 408 */
 409static int resolve_gitlink_packed_ref(char *name, int pathlen,
 410                                      const char *refname, unsigned char *sha1)
 411{
 412        int retval = -1;
 413        struct ref_entry *ref;
 414        struct ref_array *array;
 415
 416        /* being defensive: resolve_gitlink_ref() did this for us */
 417        if (pathlen < 6 || memcmp(name + pathlen - 6, "/.git/", 6))
 418                die("Oops");
 419        name[pathlen - 6] = '\0'; /* make it path to the submodule */
 420        array = get_packed_refs(name);
 421        ref = search_ref_array(array, refname);
 422        if (ref != NULL) {
 423                memcpy(sha1, ref->sha1, 20);
 424                retval = 0;
 425        }
 426        return retval;
 427}
 428
 429static int resolve_gitlink_ref_recursive(char *name, int pathlen,
 430                                         const char *refname, unsigned char *sha1,
 431                                         int recursion)
 432{
 433        int fd, len = strlen(refname);
 434        char buffer[128], *p;
 435
 436        if (recursion > MAXDEPTH || len > MAXREFLEN)
 437                return -1;
 438        memcpy(name + pathlen, refname, len+1);
 439        fd = open(name, O_RDONLY);
 440        if (fd < 0)
 441                return resolve_gitlink_packed_ref(name, pathlen, refname, sha1);
 442
 443        len = read(fd, buffer, sizeof(buffer)-1);
 444        close(fd);
 445        if (len < 0)
 446                return -1;
 447        while (len && isspace(buffer[len-1]))
 448                len--;
 449        buffer[len] = 0;
 450
 451        /* Was it a detached head or an old-fashioned symlink? */
 452        if (!get_sha1_hex(buffer, sha1))
 453                return 0;
 454
 455        /* Symref? */
 456        if (strncmp(buffer, "ref:", 4))
 457                return -1;
 458        p = buffer + 4;
 459        while (isspace(*p))
 460                p++;
 461
 462        return resolve_gitlink_ref_recursive(name, pathlen, p, sha1, recursion+1);
 463}
 464
 465int resolve_gitlink_ref(const char *path, const char *refname, unsigned char *sha1)
 466{
 467        int len = strlen(path), retval;
 468        char *gitdir;
 469        const char *tmp;
 470
 471        while (len && path[len-1] == '/')
 472                len--;
 473        if (!len)
 474                return -1;
 475        gitdir = xmalloc(len + MAXREFLEN + 8);
 476        memcpy(gitdir, path, len);
 477        memcpy(gitdir + len, "/.git", 6);
 478        len += 5;
 479
 480        tmp = read_gitfile(gitdir);
 481        if (tmp) {
 482                free(gitdir);
 483                len = strlen(tmp);
 484                gitdir = xmalloc(len + MAXREFLEN + 3);
 485                memcpy(gitdir, tmp, len);
 486        }
 487        gitdir[len] = '/';
 488        gitdir[++len] = '\0';
 489        retval = resolve_gitlink_ref_recursive(gitdir, len, refname, sha1, 0);
 490        free(gitdir);
 491        return retval;
 492}
 493
 494/*
 495 * Try to read ref from the packed references.  On success, set sha1
 496 * and return 0; otherwise, return -1.
 497 */
 498static int get_packed_ref(const char *refname, unsigned char *sha1)
 499{
 500        struct ref_array *packed = get_packed_refs(NULL);
 501        struct ref_entry *entry = search_ref_array(packed, refname);
 502        if (entry) {
 503                hashcpy(sha1, entry->sha1);
 504                return 0;
 505        }
 506        return -1;
 507}
 508
 509const char *resolve_ref(const char *refname, unsigned char *sha1, int reading, int *flag)
 510{
 511        int depth = MAXDEPTH;
 512        ssize_t len;
 513        char buffer[256];
 514        static char refname_buffer[256];
 515
 516        if (flag)
 517                *flag = 0;
 518
 519        if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
 520                return NULL;
 521
 522        for (;;) {
 523                char path[PATH_MAX];
 524                struct stat st;
 525                char *buf;
 526                int fd;
 527
 528                if (--depth < 0)
 529                        return NULL;
 530
 531                git_snpath(path, sizeof(path), "%s", refname);
 532
 533                if (lstat(path, &st) < 0) {
 534                        if (errno != ENOENT)
 535                                return NULL;
 536                        /*
 537                         * The loose reference file does not exist;
 538                         * check for a packed reference.
 539                         */
 540                        if (!get_packed_ref(refname, sha1)) {
 541                                if (flag)
 542                                        *flag |= REF_ISPACKED;
 543                                return refname;
 544                        }
 545                        /* The reference is not a packed reference, either. */
 546                        if (reading) {
 547                                return NULL;
 548                        } else {
 549                                hashclr(sha1);
 550                                return refname;
 551                        }
 552                }
 553
 554                /* Follow "normalized" - ie "refs/.." symlinks by hand */
 555                if (S_ISLNK(st.st_mode)) {
 556                        len = readlink(path, buffer, sizeof(buffer)-1);
 557                        if (len < 0)
 558                                return NULL;
 559                        buffer[len] = 0;
 560                        if (!prefixcmp(buffer, "refs/") &&
 561                                        !check_refname_format(buffer, 0)) {
 562                                strcpy(refname_buffer, buffer);
 563                                refname = refname_buffer;
 564                                if (flag)
 565                                        *flag |= REF_ISSYMREF;
 566                                continue;
 567                        }
 568                }
 569
 570                /* Is it a directory? */
 571                if (S_ISDIR(st.st_mode)) {
 572                        errno = EISDIR;
 573                        return NULL;
 574                }
 575
 576                /*
 577                 * Anything else, just open it and try to use it as
 578                 * a ref
 579                 */
 580                fd = open(path, O_RDONLY);
 581                if (fd < 0)
 582                        return NULL;
 583                len = read_in_full(fd, buffer, sizeof(buffer)-1);
 584                close(fd);
 585                if (len < 0)
 586                        return NULL;
 587                while (len && isspace(buffer[len-1]))
 588                        len--;
 589                buffer[len] = '\0';
 590
 591                /*
 592                 * Is it a symbolic ref?
 593                 */
 594                if (prefixcmp(buffer, "ref:"))
 595                        break;
 596                if (flag)
 597                        *flag |= REF_ISSYMREF;
 598                buf = buffer + 4;
 599                while (isspace(*buf))
 600                        buf++;
 601                if (check_refname_format(buf, REFNAME_ALLOW_ONELEVEL)) {
 602                        if (flag)
 603                                *flag |= REF_ISBROKEN;
 604                        return NULL;
 605                }
 606                refname = strcpy(refname_buffer, buf);
 607        }
 608        /* Please note that FETCH_HEAD has a second line containing other data. */
 609        if (get_sha1_hex(buffer, sha1) || (buffer[40] != '\0' && !isspace(buffer[40]))) {
 610                if (flag)
 611                        *flag |= REF_ISBROKEN;
 612                return NULL;
 613        }
 614        return refname;
 615}
 616
 617/* The argument to filter_refs */
 618struct ref_filter {
 619        const char *pattern;
 620        each_ref_fn *fn;
 621        void *cb_data;
 622};
 623
 624int read_ref_full(const char *refname, unsigned char *sha1, int reading, int *flags)
 625{
 626        if (resolve_ref(refname, sha1, reading, flags))
 627                return 0;
 628        return -1;
 629}
 630
 631int read_ref(const char *refname, unsigned char *sha1)
 632{
 633        return read_ref_full(refname, sha1, 1, NULL);
 634}
 635
 636#define DO_FOR_EACH_INCLUDE_BROKEN 01
 637static int do_one_ref(const char *base, each_ref_fn fn, int trim,
 638                      int flags, void *cb_data, struct ref_entry *entry)
 639{
 640        if (prefixcmp(entry->name, base))
 641                return 0;
 642
 643        if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN)) {
 644                if (entry->flag & REF_ISBROKEN)
 645                        return 0; /* ignore broken refs e.g. dangling symref */
 646                if (!has_sha1_file(entry->sha1)) {
 647                        error("%s does not point to a valid object!", entry->name);
 648                        return 0;
 649                }
 650        }
 651        current_ref = entry;
 652        return fn(entry->name + trim, entry->sha1, entry->flag, cb_data);
 653}
 654
 655static int filter_refs(const char *refname, const unsigned char *sha1, int flags,
 656                       void *data)
 657{
 658        struct ref_filter *filter = (struct ref_filter *)data;
 659        if (fnmatch(filter->pattern, refname, 0))
 660                return 0;
 661        return filter->fn(refname, sha1, flags, filter->cb_data);
 662}
 663
 664int peel_ref(const char *refname, unsigned char *sha1)
 665{
 666        int flag;
 667        unsigned char base[20];
 668        struct object *o;
 669
 670        if (current_ref && (current_ref->name == refname
 671                || !strcmp(current_ref->name, refname))) {
 672                if (current_ref->flag & REF_KNOWS_PEELED) {
 673                        hashcpy(sha1, current_ref->peeled);
 674                        return 0;
 675                }
 676                hashcpy(base, current_ref->sha1);
 677                goto fallback;
 678        }
 679
 680        if (read_ref_full(refname, base, 1, &flag))
 681                return -1;
 682
 683        if ((flag & REF_ISPACKED)) {
 684                struct ref_array *array = get_packed_refs(NULL);
 685                struct ref_entry *r = search_ref_array(array, refname);
 686
 687                if (r != NULL && r->flag & REF_KNOWS_PEELED) {
 688                        hashcpy(sha1, r->peeled);
 689                        return 0;
 690                }
 691        }
 692
 693fallback:
 694        o = parse_object(base);
 695        if (o && o->type == OBJ_TAG) {
 696                o = deref_tag(o, refname, 0);
 697                if (o) {
 698                        hashcpy(sha1, o->sha1);
 699                        return 0;
 700                }
 701        }
 702        return -1;
 703}
 704
 705static int do_for_each_ref(const char *submodule, const char *base, each_ref_fn fn,
 706                           int trim, int flags, void *cb_data)
 707{
 708        int retval = 0, i, p = 0, l = 0;
 709        struct ref_array *packed = get_packed_refs(submodule);
 710        struct ref_array *loose = get_loose_refs(submodule);
 711
 712        struct ref_array *extra = &extra_refs;
 713
 714        for (i = 0; i < extra->nr; i++)
 715                retval = do_one_ref(base, fn, trim, flags, cb_data, extra->refs[i]);
 716
 717        while (p < packed->nr && l < loose->nr) {
 718                struct ref_entry *entry;
 719                int cmp = strcmp(packed->refs[p]->name, loose->refs[l]->name);
 720                if (!cmp) {
 721                        p++;
 722                        continue;
 723                }
 724                if (cmp > 0) {
 725                        entry = loose->refs[l++];
 726                } else {
 727                        entry = packed->refs[p++];
 728                }
 729                retval = do_one_ref(base, fn, trim, flags, cb_data, entry);
 730                if (retval)
 731                        goto end_each;
 732        }
 733
 734        if (l < loose->nr) {
 735                p = l;
 736                packed = loose;
 737        }
 738
 739        for (; p < packed->nr; p++) {
 740                retval = do_one_ref(base, fn, trim, flags, cb_data, packed->refs[p]);
 741                if (retval)
 742                        goto end_each;
 743        }
 744
 745end_each:
 746        current_ref = NULL;
 747        return retval;
 748}
 749
 750
 751static int do_head_ref(const char *submodule, each_ref_fn fn, void *cb_data)
 752{
 753        unsigned char sha1[20];
 754        int flag;
 755
 756        if (submodule) {
 757                if (resolve_gitlink_ref(submodule, "HEAD", sha1) == 0)
 758                        return fn("HEAD", sha1, 0, cb_data);
 759
 760                return 0;
 761        }
 762
 763        if (!read_ref_full("HEAD", sha1, 1, &flag))
 764                return fn("HEAD", sha1, flag, cb_data);
 765
 766        return 0;
 767}
 768
 769int head_ref(each_ref_fn fn, void *cb_data)
 770{
 771        return do_head_ref(NULL, fn, cb_data);
 772}
 773
 774int head_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 775{
 776        return do_head_ref(submodule, fn, cb_data);
 777}
 778
 779int for_each_ref(each_ref_fn fn, void *cb_data)
 780{
 781        return do_for_each_ref(NULL, "", fn, 0, 0, cb_data);
 782}
 783
 784int for_each_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 785{
 786        return do_for_each_ref(submodule, "", fn, 0, 0, cb_data);
 787}
 788
 789int for_each_ref_in(const char *prefix, each_ref_fn fn, void *cb_data)
 790{
 791        return do_for_each_ref(NULL, prefix, fn, strlen(prefix), 0, cb_data);
 792}
 793
 794int for_each_ref_in_submodule(const char *submodule, const char *prefix,
 795                each_ref_fn fn, void *cb_data)
 796{
 797        return do_for_each_ref(submodule, prefix, fn, strlen(prefix), 0, cb_data);
 798}
 799
 800int for_each_tag_ref(each_ref_fn fn, void *cb_data)
 801{
 802        return for_each_ref_in("refs/tags/", fn, cb_data);
 803}
 804
 805int for_each_tag_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 806{
 807        return for_each_ref_in_submodule(submodule, "refs/tags/", fn, cb_data);
 808}
 809
 810int for_each_branch_ref(each_ref_fn fn, void *cb_data)
 811{
 812        return for_each_ref_in("refs/heads/", fn, cb_data);
 813}
 814
 815int for_each_branch_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 816{
 817        return for_each_ref_in_submodule(submodule, "refs/heads/", fn, cb_data);
 818}
 819
 820int for_each_remote_ref(each_ref_fn fn, void *cb_data)
 821{
 822        return for_each_ref_in("refs/remotes/", fn, cb_data);
 823}
 824
 825int for_each_remote_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data)
 826{
 827        return for_each_ref_in_submodule(submodule, "refs/remotes/", fn, cb_data);
 828}
 829
 830int for_each_replace_ref(each_ref_fn fn, void *cb_data)
 831{
 832        return do_for_each_ref(NULL, "refs/replace/", fn, 13, 0, cb_data);
 833}
 834
 835int head_ref_namespaced(each_ref_fn fn, void *cb_data)
 836{
 837        struct strbuf buf = STRBUF_INIT;
 838        int ret = 0;
 839        unsigned char sha1[20];
 840        int flag;
 841
 842        strbuf_addf(&buf, "%sHEAD", get_git_namespace());
 843        if (!read_ref_full(buf.buf, sha1, 1, &flag))
 844                ret = fn(buf.buf, sha1, flag, cb_data);
 845        strbuf_release(&buf);
 846
 847        return ret;
 848}
 849
 850int for_each_namespaced_ref(each_ref_fn fn, void *cb_data)
 851{
 852        struct strbuf buf = STRBUF_INIT;
 853        int ret;
 854        strbuf_addf(&buf, "%srefs/", get_git_namespace());
 855        ret = do_for_each_ref(NULL, buf.buf, fn, 0, 0, cb_data);
 856        strbuf_release(&buf);
 857        return ret;
 858}
 859
 860int for_each_glob_ref_in(each_ref_fn fn, const char *pattern,
 861        const char *prefix, void *cb_data)
 862{
 863        struct strbuf real_pattern = STRBUF_INIT;
 864        struct ref_filter filter;
 865        int ret;
 866
 867        if (!prefix && prefixcmp(pattern, "refs/"))
 868                strbuf_addstr(&real_pattern, "refs/");
 869        else if (prefix)
 870                strbuf_addstr(&real_pattern, prefix);
 871        strbuf_addstr(&real_pattern, pattern);
 872
 873        if (!has_glob_specials(pattern)) {
 874                /* Append implied '/' '*' if not present. */
 875                if (real_pattern.buf[real_pattern.len - 1] != '/')
 876                        strbuf_addch(&real_pattern, '/');
 877                /* No need to check for '*', there is none. */
 878                strbuf_addch(&real_pattern, '*');
 879        }
 880
 881        filter.pattern = real_pattern.buf;
 882        filter.fn = fn;
 883        filter.cb_data = cb_data;
 884        ret = for_each_ref(filter_refs, &filter);
 885
 886        strbuf_release(&real_pattern);
 887        return ret;
 888}
 889
 890int for_each_glob_ref(each_ref_fn fn, const char *pattern, void *cb_data)
 891{
 892        return for_each_glob_ref_in(fn, pattern, NULL, cb_data);
 893}
 894
 895int for_each_rawref(each_ref_fn fn, void *cb_data)
 896{
 897        return do_for_each_ref(NULL, "", fn, 0,
 898                               DO_FOR_EACH_INCLUDE_BROKEN, cb_data);
 899}
 900
 901/*
 902 * Make sure "ref" is something reasonable to have under ".git/refs/";
 903 * We do not like it if:
 904 *
 905 * - any path component of it begins with ".", or
 906 * - it has double dots "..", or
 907 * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 908 * - it ends with a "/".
 909 * - it ends with ".lock"
 910 * - it contains a "\" (backslash)
 911 */
 912
 913/* Return true iff ch is not allowed in reference names. */
 914static inline int bad_ref_char(int ch)
 915{
 916        if (((unsigned) ch) <= ' ' || ch == 0x7f ||
 917            ch == '~' || ch == '^' || ch == ':' || ch == '\\')
 918                return 1;
 919        /* 2.13 Pattern Matching Notation */
 920        if (ch == '*' || ch == '?' || ch == '[') /* Unsupported */
 921                return 1;
 922        return 0;
 923}
 924
 925/*
 926 * Try to read one refname component from the front of refname.  Return
 927 * the length of the component found, or -1 if the component is not
 928 * legal.
 929 */
 930static int check_refname_component(const char *refname, int flags)
 931{
 932        const char *cp;
 933        char last = '\0';
 934
 935        for (cp = refname; ; cp++) {
 936                char ch = *cp;
 937                if (ch == '\0' || ch == '/')
 938                        break;
 939                if (bad_ref_char(ch))
 940                        return -1; /* Illegal character in refname. */
 941                if (last == '.' && ch == '.')
 942                        return -1; /* Refname contains "..". */
 943                if (last == '@' && ch == '{')
 944                        return -1; /* Refname contains "@{". */
 945                last = ch;
 946        }
 947        if (cp == refname)
 948                return -1; /* Component has zero length. */
 949        if (refname[0] == '.') {
 950                if (!(flags & REFNAME_DOT_COMPONENT))
 951                        return -1; /* Component starts with '.'. */
 952                /*
 953                 * Even if leading dots are allowed, don't allow "."
 954                 * as a component (".." is prevented by a rule above).
 955                 */
 956                if (refname[1] == '\0')
 957                        return -1; /* Component equals ".". */
 958        }
 959        if (cp - refname >= 5 && !memcmp(cp - 5, ".lock", 5))
 960                return -1; /* Refname ends with ".lock". */
 961        return cp - refname;
 962}
 963
 964int check_refname_format(const char *refname, int flags)
 965{
 966        int component_len, component_count = 0;
 967
 968        while (1) {
 969                /* We are at the start of a path component. */
 970                component_len = check_refname_component(refname, flags);
 971                if (component_len < 0) {
 972                        if ((flags & REFNAME_REFSPEC_PATTERN) &&
 973                                        refname[0] == '*' &&
 974                                        (refname[1] == '\0' || refname[1] == '/')) {
 975                                /* Accept one wildcard as a full refname component. */
 976                                flags &= ~REFNAME_REFSPEC_PATTERN;
 977                                component_len = 1;
 978                        } else {
 979                                return -1;
 980                        }
 981                }
 982                component_count++;
 983                if (refname[component_len] == '\0')
 984                        break;
 985                /* Skip to next component. */
 986                refname += component_len + 1;
 987        }
 988
 989        if (refname[component_len - 1] == '.')
 990                return -1; /* Refname ends with '.'. */
 991        if (!(flags & REFNAME_ALLOW_ONELEVEL) && component_count < 2)
 992                return -1; /* Refname has only one component. */
 993        return 0;
 994}
 995
 996const char *prettify_refname(const char *name)
 997{
 998        return name + (
 999                !prefixcmp(name, "refs/heads/") ? 11 :
1000                !prefixcmp(name, "refs/tags/") ? 10 :
1001                !prefixcmp(name, "refs/remotes/") ? 13 :
1002                0);
1003}
1004
1005const char *ref_rev_parse_rules[] = {
1006        "%.*s",
1007        "refs/%.*s",
1008        "refs/tags/%.*s",
1009        "refs/heads/%.*s",
1010        "refs/remotes/%.*s",
1011        "refs/remotes/%.*s/HEAD",
1012        NULL
1013};
1014
1015int refname_match(const char *abbrev_name, const char *full_name, const char **rules)
1016{
1017        const char **p;
1018        const int abbrev_name_len = strlen(abbrev_name);
1019
1020        for (p = rules; *p; p++) {
1021                if (!strcmp(full_name, mkpath(*p, abbrev_name_len, abbrev_name))) {
1022                        return 1;
1023                }
1024        }
1025
1026        return 0;
1027}
1028
1029static struct ref_lock *verify_lock(struct ref_lock *lock,
1030        const unsigned char *old_sha1, int mustexist)
1031{
1032        if (read_ref_full(lock->ref_name, lock->old_sha1, mustexist, NULL)) {
1033                error("Can't verify ref %s", lock->ref_name);
1034                unlock_ref(lock);
1035                return NULL;
1036        }
1037        if (hashcmp(lock->old_sha1, old_sha1)) {
1038                error("Ref %s is at %s but expected %s", lock->ref_name,
1039                        sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
1040                unlock_ref(lock);
1041                return NULL;
1042        }
1043        return lock;
1044}
1045
1046static int remove_empty_directories(const char *file)
1047{
1048        /* we want to create a file but there is a directory there;
1049         * if that is an empty directory (or a directory that contains
1050         * only empty directories), remove them.
1051         */
1052        struct strbuf path;
1053        int result;
1054
1055        strbuf_init(&path, 20);
1056        strbuf_addstr(&path, file);
1057
1058        result = remove_dir_recursively(&path, REMOVE_DIR_EMPTY_ONLY);
1059
1060        strbuf_release(&path);
1061
1062        return result;
1063}
1064
1065/*
1066 * Return true iff a reference named refname could be created without
1067 * conflicting with the name of an existing reference.  If oldrefname
1068 * is non-NULL, ignore potential conflicts with oldrefname (e.g.,
1069 * because oldrefname is scheduled for deletion in the same
1070 * operation).
1071 */
1072static int is_refname_available(const char *refname, const char *oldrefname,
1073                                struct ref_array *array)
1074{
1075        int i, namlen = strlen(refname); /* e.g. 'foo/bar' */
1076        for (i = 0; i < array->nr; i++ ) {
1077                struct ref_entry *entry = array->refs[i];
1078                /* entry->name could be 'foo' or 'foo/bar/baz' */
1079                if (!oldrefname || strcmp(oldrefname, entry->name)) {
1080                        int len = strlen(entry->name);
1081                        int cmplen = (namlen < len) ? namlen : len;
1082                        const char *lead = (namlen < len) ? entry->name : refname;
1083                        if (!strncmp(refname, entry->name, cmplen) &&
1084                            lead[cmplen] == '/') {
1085                                error("'%s' exists; cannot create '%s'",
1086                                      entry->name, refname);
1087                                return 0;
1088                        }
1089                }
1090        }
1091        return 1;
1092}
1093
1094/*
1095 * *string and *len will only be substituted, and *string returned (for
1096 * later free()ing) if the string passed in is a magic short-hand form
1097 * to name a branch.
1098 */
1099static char *substitute_branch_name(const char **string, int *len)
1100{
1101        struct strbuf buf = STRBUF_INIT;
1102        int ret = interpret_branch_name(*string, &buf);
1103
1104        if (ret == *len) {
1105                size_t size;
1106                *string = strbuf_detach(&buf, &size);
1107                *len = size;
1108                return (char *)*string;
1109        }
1110
1111        return NULL;
1112}
1113
1114int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
1115{
1116        char *last_branch = substitute_branch_name(&str, &len);
1117        const char **p, *r;
1118        int refs_found = 0;
1119
1120        *ref = NULL;
1121        for (p = ref_rev_parse_rules; *p; p++) {
1122                char fullref[PATH_MAX];
1123                unsigned char sha1_from_ref[20];
1124                unsigned char *this_result;
1125                int flag;
1126
1127                this_result = refs_found ? sha1_from_ref : sha1;
1128                mksnpath(fullref, sizeof(fullref), *p, len, str);
1129                r = resolve_ref(fullref, this_result, 1, &flag);
1130                if (r) {
1131                        if (!refs_found++)
1132                                *ref = xstrdup(r);
1133                        if (!warn_ambiguous_refs)
1134                                break;
1135                } else if ((flag & REF_ISSYMREF) && strcmp(fullref, "HEAD")) {
1136                        warning("ignoring dangling symref %s.", fullref);
1137                } else if ((flag & REF_ISBROKEN) && strchr(fullref, '/')) {
1138                        warning("ignoring broken ref %s.", fullref);
1139                }
1140        }
1141        free(last_branch);
1142        return refs_found;
1143}
1144
1145int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
1146{
1147        char *last_branch = substitute_branch_name(&str, &len);
1148        const char **p;
1149        int logs_found = 0;
1150
1151        *log = NULL;
1152        for (p = ref_rev_parse_rules; *p; p++) {
1153                struct stat st;
1154                unsigned char hash[20];
1155                char path[PATH_MAX];
1156                const char *ref, *it;
1157
1158                mksnpath(path, sizeof(path), *p, len, str);
1159                ref = resolve_ref(path, hash, 1, NULL);
1160                if (!ref)
1161                        continue;
1162                if (!stat(git_path("logs/%s", path), &st) &&
1163                    S_ISREG(st.st_mode))
1164                        it = path;
1165                else if (strcmp(ref, path) &&
1166                         !stat(git_path("logs/%s", ref), &st) &&
1167                         S_ISREG(st.st_mode))
1168                        it = ref;
1169                else
1170                        continue;
1171                if (!logs_found++) {
1172                        *log = xstrdup(it);
1173                        hashcpy(sha1, hash);
1174                }
1175                if (!warn_ambiguous_refs)
1176                        break;
1177        }
1178        free(last_branch);
1179        return logs_found;
1180}
1181
1182static struct ref_lock *lock_ref_sha1_basic(const char *refname,
1183                                            const unsigned char *old_sha1,
1184                                            int flags, int *type_p)
1185{
1186        char *ref_file;
1187        const char *orig_refname = refname;
1188        struct ref_lock *lock;
1189        int last_errno = 0;
1190        int type, lflags;
1191        int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
1192        int missing = 0;
1193
1194        lock = xcalloc(1, sizeof(struct ref_lock));
1195        lock->lock_fd = -1;
1196
1197        refname = resolve_ref(refname, lock->old_sha1, mustexist, &type);
1198        if (!refname && errno == EISDIR) {
1199                /* we are trying to lock foo but we used to
1200                 * have foo/bar which now does not exist;
1201                 * it is normal for the empty directory 'foo'
1202                 * to remain.
1203                 */
1204                ref_file = git_path("%s", orig_refname);
1205                if (remove_empty_directories(ref_file)) {
1206                        last_errno = errno;
1207                        error("there are still refs under '%s'", orig_refname);
1208                        goto error_return;
1209                }
1210                refname = resolve_ref(orig_refname, lock->old_sha1, mustexist, &type);
1211        }
1212        if (type_p)
1213            *type_p = type;
1214        if (!refname) {
1215                last_errno = errno;
1216                error("unable to resolve reference %s: %s",
1217                        orig_refname, strerror(errno));
1218                goto error_return;
1219        }
1220        missing = is_null_sha1(lock->old_sha1);
1221        /* When the ref did not exist and we are creating it,
1222         * make sure there is no existing ref that is packed
1223         * whose name begins with our refname, nor a ref whose
1224         * name is a proper prefix of our refname.
1225         */
1226        if (missing &&
1227             !is_refname_available(refname, NULL, get_packed_refs(NULL))) {
1228                last_errno = ENOTDIR;
1229                goto error_return;
1230        }
1231
1232        lock->lk = xcalloc(1, sizeof(struct lock_file));
1233
1234        lflags = LOCK_DIE_ON_ERROR;
1235        if (flags & REF_NODEREF) {
1236                refname = orig_refname;
1237                lflags |= LOCK_NODEREF;
1238        }
1239        lock->ref_name = xstrdup(refname);
1240        lock->orig_ref_name = xstrdup(orig_refname);
1241        ref_file = git_path("%s", refname);
1242        if (missing)
1243                lock->force_write = 1;
1244        if ((flags & REF_NODEREF) && (type & REF_ISSYMREF))
1245                lock->force_write = 1;
1246
1247        if (safe_create_leading_directories(ref_file)) {
1248                last_errno = errno;
1249                error("unable to create directory for %s", ref_file);
1250                goto error_return;
1251        }
1252
1253        lock->lock_fd = hold_lock_file_for_update(lock->lk, ref_file, lflags);
1254        return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
1255
1256 error_return:
1257        unlock_ref(lock);
1258        errno = last_errno;
1259        return NULL;
1260}
1261
1262struct ref_lock *lock_ref_sha1(const char *refname, const unsigned char *old_sha1)
1263{
1264        char refpath[PATH_MAX];
1265        if (check_refname_format(refname, 0))
1266                return NULL;
1267        strcpy(refpath, mkpath("refs/%s", refname));
1268        return lock_ref_sha1_basic(refpath, old_sha1, 0, NULL);
1269}
1270
1271struct ref_lock *lock_any_ref_for_update(const char *refname,
1272                                         const unsigned char *old_sha1, int flags)
1273{
1274        if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
1275                return NULL;
1276        return lock_ref_sha1_basic(refname, old_sha1, flags, NULL);
1277}
1278
1279static struct lock_file packlock;
1280
1281static int repack_without_ref(const char *refname)
1282{
1283        struct ref_array *packed;
1284        struct ref_entry *ref;
1285        int fd, i;
1286
1287        packed = get_packed_refs(NULL);
1288        ref = search_ref_array(packed, refname);
1289        if (ref == NULL)
1290                return 0;
1291        fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"), 0);
1292        if (fd < 0) {
1293                unable_to_lock_error(git_path("packed-refs"), errno);
1294                return error("cannot delete '%s' from packed refs", refname);
1295        }
1296
1297        for (i = 0; i < packed->nr; i++) {
1298                char line[PATH_MAX + 100];
1299                int len;
1300
1301                ref = packed->refs[i];
1302
1303                if (!strcmp(refname, ref->name))
1304                        continue;
1305                len = snprintf(line, sizeof(line), "%s %s\n",
1306                               sha1_to_hex(ref->sha1), ref->name);
1307                /* this should not happen but just being defensive */
1308                if (len > sizeof(line))
1309                        die("too long a refname '%s'", ref->name);
1310                write_or_die(fd, line, len);
1311        }
1312        return commit_lock_file(&packlock);
1313}
1314
1315int delete_ref(const char *refname, const unsigned char *sha1, int delopt)
1316{
1317        struct ref_lock *lock;
1318        int err, i = 0, ret = 0, flag = 0;
1319
1320        lock = lock_ref_sha1_basic(refname, sha1, 0, &flag);
1321        if (!lock)
1322                return 1;
1323        if (!(flag & REF_ISPACKED) || flag & REF_ISSYMREF) {
1324                /* loose */
1325                const char *path;
1326
1327                if (!(delopt & REF_NODEREF)) {
1328                        i = strlen(lock->lk->filename) - 5; /* .lock */
1329                        lock->lk->filename[i] = 0;
1330                        path = lock->lk->filename;
1331                } else {
1332                        path = git_path("%s", refname);
1333                }
1334                err = unlink_or_warn(path);
1335                if (err && errno != ENOENT)
1336                        ret = 1;
1337
1338                if (!(delopt & REF_NODEREF))
1339                        lock->lk->filename[i] = '.';
1340        }
1341        /* removing the loose one could have resurrected an earlier
1342         * packed one.  Also, if it was not loose we need to repack
1343         * without it.
1344         */
1345        ret |= repack_without_ref(refname);
1346
1347        unlink_or_warn(git_path("logs/%s", lock->ref_name));
1348        invalidate_ref_cache(NULL);
1349        unlock_ref(lock);
1350        return ret;
1351}
1352
1353/*
1354 * People using contrib's git-new-workdir have .git/logs/refs ->
1355 * /some/other/path/.git/logs/refs, and that may live on another device.
1356 *
1357 * IOW, to avoid cross device rename errors, the temporary renamed log must
1358 * live into logs/refs.
1359 */
1360#define TMP_RENAMED_LOG  "logs/refs/.tmp-renamed-log"
1361
1362int rename_ref(const char *oldrefname, const char *newrefname, const char *logmsg)
1363{
1364        unsigned char sha1[20], orig_sha1[20];
1365        int flag = 0, logmoved = 0;
1366        struct ref_lock *lock;
1367        struct stat loginfo;
1368        int log = !lstat(git_path("logs/%s", oldrefname), &loginfo);
1369        const char *symref = NULL;
1370
1371        if (log && S_ISLNK(loginfo.st_mode))
1372                return error("reflog for %s is a symlink", oldrefname);
1373
1374        symref = resolve_ref(oldrefname, orig_sha1, 1, &flag);
1375        if (flag & REF_ISSYMREF)
1376                return error("refname %s is a symbolic ref, renaming it is not supported",
1377                        oldrefname);
1378        if (!symref)
1379                return error("refname %s not found", oldrefname);
1380
1381        if (!is_refname_available(newrefname, oldrefname, get_packed_refs(NULL)))
1382                return 1;
1383
1384        if (!is_refname_available(newrefname, oldrefname, get_loose_refs(NULL)))
1385                return 1;
1386
1387        if (log && rename(git_path("logs/%s", oldrefname), git_path(TMP_RENAMED_LOG)))
1388                return error("unable to move logfile logs/%s to "TMP_RENAMED_LOG": %s",
1389                        oldrefname, strerror(errno));
1390
1391        if (delete_ref(oldrefname, orig_sha1, REF_NODEREF)) {
1392                error("unable to delete old %s", oldrefname);
1393                goto rollback;
1394        }
1395
1396        if (!read_ref_full(newrefname, sha1, 1, &flag) &&
1397            delete_ref(newrefname, sha1, REF_NODEREF)) {
1398                if (errno==EISDIR) {
1399                        if (remove_empty_directories(git_path("%s", newrefname))) {
1400                                error("Directory not empty: %s", newrefname);
1401                                goto rollback;
1402                        }
1403                } else {
1404                        error("unable to delete existing %s", newrefname);
1405                        goto rollback;
1406                }
1407        }
1408
1409        if (log && safe_create_leading_directories(git_path("logs/%s", newrefname))) {
1410                error("unable to create directory for %s", newrefname);
1411                goto rollback;
1412        }
1413
1414 retry:
1415        if (log && rename(git_path(TMP_RENAMED_LOG), git_path("logs/%s", newrefname))) {
1416                if (errno==EISDIR || errno==ENOTDIR) {
1417                        /*
1418                         * rename(a, b) when b is an existing
1419                         * directory ought to result in ISDIR, but
1420                         * Solaris 5.8 gives ENOTDIR.  Sheesh.
1421                         */
1422                        if (remove_empty_directories(git_path("logs/%s", newrefname))) {
1423                                error("Directory not empty: logs/%s", newrefname);
1424                                goto rollback;
1425                        }
1426                        goto retry;
1427                } else {
1428                        error("unable to move logfile "TMP_RENAMED_LOG" to logs/%s: %s",
1429                                newrefname, strerror(errno));
1430                        goto rollback;
1431                }
1432        }
1433        logmoved = log;
1434
1435        lock = lock_ref_sha1_basic(newrefname, NULL, 0, NULL);
1436        if (!lock) {
1437                error("unable to lock %s for update", newrefname);
1438                goto rollback;
1439        }
1440        lock->force_write = 1;
1441        hashcpy(lock->old_sha1, orig_sha1);
1442        if (write_ref_sha1(lock, orig_sha1, logmsg)) {
1443                error("unable to write current sha1 into %s", newrefname);
1444                goto rollback;
1445        }
1446
1447        return 0;
1448
1449 rollback:
1450        lock = lock_ref_sha1_basic(oldrefname, NULL, 0, NULL);
1451        if (!lock) {
1452                error("unable to lock %s for rollback", oldrefname);
1453                goto rollbacklog;
1454        }
1455
1456        lock->force_write = 1;
1457        flag = log_all_ref_updates;
1458        log_all_ref_updates = 0;
1459        if (write_ref_sha1(lock, orig_sha1, NULL))
1460                error("unable to write current sha1 into %s", oldrefname);
1461        log_all_ref_updates = flag;
1462
1463 rollbacklog:
1464        if (logmoved && rename(git_path("logs/%s", newrefname), git_path("logs/%s", oldrefname)))
1465                error("unable to restore logfile %s from %s: %s",
1466                        oldrefname, newrefname, strerror(errno));
1467        if (!logmoved && log &&
1468            rename(git_path(TMP_RENAMED_LOG), git_path("logs/%s", oldrefname)))
1469                error("unable to restore logfile %s from "TMP_RENAMED_LOG": %s",
1470                        oldrefname, strerror(errno));
1471
1472        return 1;
1473}
1474
1475int close_ref(struct ref_lock *lock)
1476{
1477        if (close_lock_file(lock->lk))
1478                return -1;
1479        lock->lock_fd = -1;
1480        return 0;
1481}
1482
1483int commit_ref(struct ref_lock *lock)
1484{
1485        if (commit_lock_file(lock->lk))
1486                return -1;
1487        lock->lock_fd = -1;
1488        return 0;
1489}
1490
1491void unlock_ref(struct ref_lock *lock)
1492{
1493        /* Do not free lock->lk -- atexit() still looks at them */
1494        if (lock->lk)
1495                rollback_lock_file(lock->lk);
1496        free(lock->ref_name);
1497        free(lock->orig_ref_name);
1498        free(lock);
1499}
1500
1501/*
1502 * copy the reflog message msg to buf, which has been allocated sufficiently
1503 * large, while cleaning up the whitespaces.  Especially, convert LF to space,
1504 * because reflog file is one line per entry.
1505 */
1506static int copy_msg(char *buf, const char *msg)
1507{
1508        char *cp = buf;
1509        char c;
1510        int wasspace = 1;
1511
1512        *cp++ = '\t';
1513        while ((c = *msg++)) {
1514                if (wasspace && isspace(c))
1515                        continue;
1516                wasspace = isspace(c);
1517                if (wasspace)
1518                        c = ' ';
1519                *cp++ = c;
1520        }
1521        while (buf < cp && isspace(cp[-1]))
1522                cp--;
1523        *cp++ = '\n';
1524        return cp - buf;
1525}
1526
1527int log_ref_setup(const char *refname, char *logfile, int bufsize)
1528{
1529        int logfd, oflags = O_APPEND | O_WRONLY;
1530
1531        git_snpath(logfile, bufsize, "logs/%s", refname);
1532        if (log_all_ref_updates &&
1533            (!prefixcmp(refname, "refs/heads/") ||
1534             !prefixcmp(refname, "refs/remotes/") ||
1535             !prefixcmp(refname, "refs/notes/") ||
1536             !strcmp(refname, "HEAD"))) {
1537                if (safe_create_leading_directories(logfile) < 0)
1538                        return error("unable to create directory for %s",
1539                                     logfile);
1540                oflags |= O_CREAT;
1541        }
1542
1543        logfd = open(logfile, oflags, 0666);
1544        if (logfd < 0) {
1545                if (!(oflags & O_CREAT) && errno == ENOENT)
1546                        return 0;
1547
1548                if ((oflags & O_CREAT) && errno == EISDIR) {
1549                        if (remove_empty_directories(logfile)) {
1550                                return error("There are still logs under '%s'",
1551                                             logfile);
1552                        }
1553                        logfd = open(logfile, oflags, 0666);
1554                }
1555
1556                if (logfd < 0)
1557                        return error("Unable to append to %s: %s",
1558                                     logfile, strerror(errno));
1559        }
1560
1561        adjust_shared_perm(logfile);
1562        close(logfd);
1563        return 0;
1564}
1565
1566static int log_ref_write(const char *refname, const unsigned char *old_sha1,
1567                         const unsigned char *new_sha1, const char *msg)
1568{
1569        int logfd, result, written, oflags = O_APPEND | O_WRONLY;
1570        unsigned maxlen, len;
1571        int msglen;
1572        char log_file[PATH_MAX];
1573        char *logrec;
1574        const char *committer;
1575
1576        if (log_all_ref_updates < 0)
1577                log_all_ref_updates = !is_bare_repository();
1578
1579        result = log_ref_setup(refname, log_file, sizeof(log_file));
1580        if (result)
1581                return result;
1582
1583        logfd = open(log_file, oflags);
1584        if (logfd < 0)
1585                return 0;
1586        msglen = msg ? strlen(msg) : 0;
1587        committer = git_committer_info(0);
1588        maxlen = strlen(committer) + msglen + 100;
1589        logrec = xmalloc(maxlen);
1590        len = sprintf(logrec, "%s %s %s\n",
1591                      sha1_to_hex(old_sha1),
1592                      sha1_to_hex(new_sha1),
1593                      committer);
1594        if (msglen)
1595                len += copy_msg(logrec + len - 1, msg) - 1;
1596        written = len <= maxlen ? write_in_full(logfd, logrec, len) : -1;
1597        free(logrec);
1598        if (close(logfd) != 0 || written != len)
1599                return error("Unable to append to %s", log_file);
1600        return 0;
1601}
1602
1603static int is_branch(const char *refname)
1604{
1605        return !strcmp(refname, "HEAD") || !prefixcmp(refname, "refs/heads/");
1606}
1607
1608int write_ref_sha1(struct ref_lock *lock,
1609        const unsigned char *sha1, const char *logmsg)
1610{
1611        static char term = '\n';
1612        struct object *o;
1613
1614        if (!lock)
1615                return -1;
1616        if (!lock->force_write && !hashcmp(lock->old_sha1, sha1)) {
1617                unlock_ref(lock);
1618                return 0;
1619        }
1620        o = parse_object(sha1);
1621        if (!o) {
1622                error("Trying to write ref %s with nonexistent object %s",
1623                        lock->ref_name, sha1_to_hex(sha1));
1624                unlock_ref(lock);
1625                return -1;
1626        }
1627        if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
1628                error("Trying to write non-commit object %s to branch %s",
1629                        sha1_to_hex(sha1), lock->ref_name);
1630                unlock_ref(lock);
1631                return -1;
1632        }
1633        if (write_in_full(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
1634            write_in_full(lock->lock_fd, &term, 1) != 1
1635                || close_ref(lock) < 0) {
1636                error("Couldn't write %s", lock->lk->filename);
1637                unlock_ref(lock);
1638                return -1;
1639        }
1640        clear_loose_ref_cache(get_ref_cache(NULL));
1641        if (log_ref_write(lock->ref_name, lock->old_sha1, sha1, logmsg) < 0 ||
1642            (strcmp(lock->ref_name, lock->orig_ref_name) &&
1643             log_ref_write(lock->orig_ref_name, lock->old_sha1, sha1, logmsg) < 0)) {
1644                unlock_ref(lock);
1645                return -1;
1646        }
1647        if (strcmp(lock->orig_ref_name, "HEAD") != 0) {
1648                /*
1649                 * Special hack: If a branch is updated directly and HEAD
1650                 * points to it (may happen on the remote side of a push
1651                 * for example) then logically the HEAD reflog should be
1652                 * updated too.
1653                 * A generic solution implies reverse symref information,
1654                 * but finding all symrefs pointing to the given branch
1655                 * would be rather costly for this rare event (the direct
1656                 * update of a branch) to be worth it.  So let's cheat and
1657                 * check with HEAD only which should cover 99% of all usage
1658                 * scenarios (even 100% of the default ones).
1659                 */
1660                unsigned char head_sha1[20];
1661                int head_flag;
1662                const char *head_ref;
1663                head_ref = resolve_ref("HEAD", head_sha1, 1, &head_flag);
1664                if (head_ref && (head_flag & REF_ISSYMREF) &&
1665                    !strcmp(head_ref, lock->ref_name))
1666                        log_ref_write("HEAD", lock->old_sha1, sha1, logmsg);
1667        }
1668        if (commit_ref(lock)) {
1669                error("Couldn't set %s", lock->ref_name);
1670                unlock_ref(lock);
1671                return -1;
1672        }
1673        unlock_ref(lock);
1674        return 0;
1675}
1676
1677int create_symref(const char *ref_target, const char *refs_heads_master,
1678                  const char *logmsg)
1679{
1680        const char *lockpath;
1681        char ref[1000];
1682        int fd, len, written;
1683        char *git_HEAD = git_pathdup("%s", ref_target);
1684        unsigned char old_sha1[20], new_sha1[20];
1685
1686        if (logmsg && read_ref(ref_target, old_sha1))
1687                hashclr(old_sha1);
1688
1689        if (safe_create_leading_directories(git_HEAD) < 0)
1690                return error("unable to create directory for %s", git_HEAD);
1691
1692#ifndef NO_SYMLINK_HEAD
1693        if (prefer_symlink_refs) {
1694                unlink(git_HEAD);
1695                if (!symlink(refs_heads_master, git_HEAD))
1696                        goto done;
1697                fprintf(stderr, "no symlink - falling back to symbolic ref\n");
1698        }
1699#endif
1700
1701        len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
1702        if (sizeof(ref) <= len) {
1703                error("refname too long: %s", refs_heads_master);
1704                goto error_free_return;
1705        }
1706        lockpath = mkpath("%s.lock", git_HEAD);
1707        fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
1708        if (fd < 0) {
1709                error("Unable to open %s for writing", lockpath);
1710                goto error_free_return;
1711        }
1712        written = write_in_full(fd, ref, len);
1713        if (close(fd) != 0 || written != len) {
1714                error("Unable to write to %s", lockpath);
1715                goto error_unlink_return;
1716        }
1717        if (rename(lockpath, git_HEAD) < 0) {
1718                error("Unable to create %s", git_HEAD);
1719                goto error_unlink_return;
1720        }
1721        if (adjust_shared_perm(git_HEAD)) {
1722                error("Unable to fix permissions on %s", lockpath);
1723        error_unlink_return:
1724                unlink_or_warn(lockpath);
1725        error_free_return:
1726                free(git_HEAD);
1727                return -1;
1728        }
1729
1730#ifndef NO_SYMLINK_HEAD
1731        done:
1732#endif
1733        if (logmsg && !read_ref(refs_heads_master, new_sha1))
1734                log_ref_write(ref_target, old_sha1, new_sha1, logmsg);
1735
1736        free(git_HEAD);
1737        return 0;
1738}
1739
1740static char *ref_msg(const char *line, const char *endp)
1741{
1742        const char *ep;
1743        line += 82;
1744        ep = memchr(line, '\n', endp - line);
1745        if (!ep)
1746                ep = endp;
1747        return xmemdupz(line, ep - line);
1748}
1749
1750int read_ref_at(const char *refname, unsigned long at_time, int cnt,
1751                unsigned char *sha1, char **msg,
1752                unsigned long *cutoff_time, int *cutoff_tz, int *cutoff_cnt)
1753{
1754        const char *logfile, *logdata, *logend, *rec, *lastgt, *lastrec;
1755        char *tz_c;
1756        int logfd, tz, reccnt = 0;
1757        struct stat st;
1758        unsigned long date;
1759        unsigned char logged_sha1[20];
1760        void *log_mapped;
1761        size_t mapsz;
1762
1763        logfile = git_path("logs/%s", refname);
1764        logfd = open(logfile, O_RDONLY, 0);
1765        if (logfd < 0)
1766                die_errno("Unable to read log '%s'", logfile);
1767        fstat(logfd, &st);
1768        if (!st.st_size)
1769                die("Log %s is empty.", logfile);
1770        mapsz = xsize_t(st.st_size);
1771        log_mapped = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, logfd, 0);
1772        logdata = log_mapped;
1773        close(logfd);
1774
1775        lastrec = NULL;
1776        rec = logend = logdata + st.st_size;
1777        while (logdata < rec) {
1778                reccnt++;
1779                if (logdata < rec && *(rec-1) == '\n')
1780                        rec--;
1781                lastgt = NULL;
1782                while (logdata < rec && *(rec-1) != '\n') {
1783                        rec--;
1784                        if (*rec == '>')
1785                                lastgt = rec;
1786                }
1787                if (!lastgt)
1788                        die("Log %s is corrupt.", logfile);
1789                date = strtoul(lastgt + 1, &tz_c, 10);
1790                if (date <= at_time || cnt == 0) {
1791                        tz = strtoul(tz_c, NULL, 10);
1792                        if (msg)
1793                                *msg = ref_msg(rec, logend);
1794                        if (cutoff_time)
1795                                *cutoff_time = date;
1796                        if (cutoff_tz)
1797                                *cutoff_tz = tz;
1798                        if (cutoff_cnt)
1799                                *cutoff_cnt = reccnt - 1;
1800                        if (lastrec) {
1801                                if (get_sha1_hex(lastrec, logged_sha1))
1802                                        die("Log %s is corrupt.", logfile);
1803                                if (get_sha1_hex(rec + 41, sha1))
1804                                        die("Log %s is corrupt.", logfile);
1805                                if (hashcmp(logged_sha1, sha1)) {
1806                                        warning("Log %s has gap after %s.",
1807                                                logfile, show_date(date, tz, DATE_RFC2822));
1808                                }
1809                        }
1810                        else if (date == at_time) {
1811                                if (get_sha1_hex(rec + 41, sha1))
1812                                        die("Log %s is corrupt.", logfile);
1813                        }
1814                        else {
1815                                if (get_sha1_hex(rec + 41, logged_sha1))
1816                                        die("Log %s is corrupt.", logfile);
1817                                if (hashcmp(logged_sha1, sha1)) {
1818                                        warning("Log %s unexpectedly ended on %s.",
1819                                                logfile, show_date(date, tz, DATE_RFC2822));
1820                                }
1821                        }
1822                        munmap(log_mapped, mapsz);
1823                        return 0;
1824                }
1825                lastrec = rec;
1826                if (cnt > 0)
1827                        cnt--;
1828        }
1829
1830        rec = logdata;
1831        while (rec < logend && *rec != '>' && *rec != '\n')
1832                rec++;
1833        if (rec == logend || *rec == '\n')
1834                die("Log %s is corrupt.", logfile);
1835        date = strtoul(rec + 1, &tz_c, 10);
1836        tz = strtoul(tz_c, NULL, 10);
1837        if (get_sha1_hex(logdata, sha1))
1838                die("Log %s is corrupt.", logfile);
1839        if (is_null_sha1(sha1)) {
1840                if (get_sha1_hex(logdata + 41, sha1))
1841                        die("Log %s is corrupt.", logfile);
1842        }
1843        if (msg)
1844                *msg = ref_msg(logdata, logend);
1845        munmap(log_mapped, mapsz);
1846
1847        if (cutoff_time)
1848                *cutoff_time = date;
1849        if (cutoff_tz)
1850                *cutoff_tz = tz;
1851        if (cutoff_cnt)
1852                *cutoff_cnt = reccnt;
1853        return 1;
1854}
1855
1856int for_each_recent_reflog_ent(const char *refname, each_reflog_ent_fn fn, long ofs, void *cb_data)
1857{
1858        const char *logfile;
1859        FILE *logfp;
1860        struct strbuf sb = STRBUF_INIT;
1861        int ret = 0;
1862
1863        logfile = git_path("logs/%s", refname);
1864        logfp = fopen(logfile, "r");
1865        if (!logfp)
1866                return -1;
1867
1868        if (ofs) {
1869                struct stat statbuf;
1870                if (fstat(fileno(logfp), &statbuf) ||
1871                    statbuf.st_size < ofs ||
1872                    fseek(logfp, -ofs, SEEK_END) ||
1873                    strbuf_getwholeline(&sb, logfp, '\n')) {
1874                        fclose(logfp);
1875                        strbuf_release(&sb);
1876                        return -1;
1877                }
1878        }
1879
1880        while (!strbuf_getwholeline(&sb, logfp, '\n')) {
1881                unsigned char osha1[20], nsha1[20];
1882                char *email_end, *message;
1883                unsigned long timestamp;
1884                int tz;
1885
1886                /* old SP new SP name <email> SP time TAB msg LF */
1887                if (sb.len < 83 || sb.buf[sb.len - 1] != '\n' ||
1888                    get_sha1_hex(sb.buf, osha1) || sb.buf[40] != ' ' ||
1889                    get_sha1_hex(sb.buf + 41, nsha1) || sb.buf[81] != ' ' ||
1890                    !(email_end = strchr(sb.buf + 82, '>')) ||
1891                    email_end[1] != ' ' ||
1892                    !(timestamp = strtoul(email_end + 2, &message, 10)) ||
1893                    !message || message[0] != ' ' ||
1894                    (message[1] != '+' && message[1] != '-') ||
1895                    !isdigit(message[2]) || !isdigit(message[3]) ||
1896                    !isdigit(message[4]) || !isdigit(message[5]))
1897                        continue; /* corrupt? */
1898                email_end[1] = '\0';
1899                tz = strtol(message + 1, NULL, 10);
1900                if (message[6] != '\t')
1901                        message += 6;
1902                else
1903                        message += 7;
1904                ret = fn(osha1, nsha1, sb.buf + 82, timestamp, tz, message,
1905                         cb_data);
1906                if (ret)
1907                        break;
1908        }
1909        fclose(logfp);
1910        strbuf_release(&sb);
1911        return ret;
1912}
1913
1914int for_each_reflog_ent(const char *refname, each_reflog_ent_fn fn, void *cb_data)
1915{
1916        return for_each_recent_reflog_ent(refname, fn, 0, cb_data);
1917}
1918
1919static int do_for_each_reflog(const char *base, each_ref_fn fn, void *cb_data)
1920{
1921        DIR *dir = opendir(git_path("logs/%s", base));
1922        int retval = 0;
1923
1924        if (dir) {
1925                struct dirent *de;
1926                int baselen = strlen(base);
1927                char *log = xmalloc(baselen + 257);
1928
1929                memcpy(log, base, baselen);
1930                if (baselen && base[baselen-1] != '/')
1931                        log[baselen++] = '/';
1932
1933                while ((de = readdir(dir)) != NULL) {
1934                        struct stat st;
1935                        int namelen;
1936
1937                        if (de->d_name[0] == '.')
1938                                continue;
1939                        namelen = strlen(de->d_name);
1940                        if (namelen > 255)
1941                                continue;
1942                        if (has_extension(de->d_name, ".lock"))
1943                                continue;
1944                        memcpy(log + baselen, de->d_name, namelen+1);
1945                        if (stat(git_path("logs/%s", log), &st) < 0)
1946                                continue;
1947                        if (S_ISDIR(st.st_mode)) {
1948                                retval = do_for_each_reflog(log, fn, cb_data);
1949                        } else {
1950                                unsigned char sha1[20];
1951                                if (read_ref_full(log, sha1, 0, NULL))
1952                                        retval = error("bad ref for %s", log);
1953                                else
1954                                        retval = fn(log, sha1, 0, cb_data);
1955                        }
1956                        if (retval)
1957                                break;
1958                }
1959                free(log);
1960                closedir(dir);
1961        }
1962        else if (*base)
1963                return errno;
1964        return retval;
1965}
1966
1967int for_each_reflog(each_ref_fn fn, void *cb_data)
1968{
1969        return do_for_each_reflog("", fn, cb_data);
1970}
1971
1972int update_ref(const char *action, const char *refname,
1973                const unsigned char *sha1, const unsigned char *oldval,
1974                int flags, enum action_on_err onerr)
1975{
1976        static struct ref_lock *lock;
1977        lock = lock_any_ref_for_update(refname, oldval, flags);
1978        if (!lock) {
1979                const char *str = "Cannot lock the ref '%s'.";
1980                switch (onerr) {
1981                case MSG_ON_ERR: error(str, refname); break;
1982                case DIE_ON_ERR: die(str, refname); break;
1983                case QUIET_ON_ERR: break;
1984                }
1985                return 1;
1986        }
1987        if (write_ref_sha1(lock, sha1, action) < 0) {
1988                const char *str = "Cannot update the ref '%s'.";
1989                switch (onerr) {
1990                case MSG_ON_ERR: error(str, refname); break;
1991                case DIE_ON_ERR: die(str, refname); break;
1992                case QUIET_ON_ERR: break;
1993                }
1994                return 1;
1995        }
1996        return 0;
1997}
1998
1999int ref_exists(const char *refname)
2000{
2001        unsigned char sha1[20];
2002        return !!resolve_ref(refname, sha1, 1, NULL);
2003}
2004
2005struct ref *find_ref_by_name(const struct ref *list, const char *name)
2006{
2007        for ( ; list; list = list->next)
2008                if (!strcmp(list->name, name))
2009                        return (struct ref *)list;
2010        return NULL;
2011}
2012
2013/*
2014 * generate a format suitable for scanf from a ref_rev_parse_rules
2015 * rule, that is replace the "%.*s" spec with a "%s" spec
2016 */
2017static void gen_scanf_fmt(char *scanf_fmt, const char *rule)
2018{
2019        char *spec;
2020
2021        spec = strstr(rule, "%.*s");
2022        if (!spec || strstr(spec + 4, "%.*s"))
2023                die("invalid rule in ref_rev_parse_rules: %s", rule);
2024
2025        /* copy all until spec */
2026        strncpy(scanf_fmt, rule, spec - rule);
2027        scanf_fmt[spec - rule] = '\0';
2028        /* copy new spec */
2029        strcat(scanf_fmt, "%s");
2030        /* copy remaining rule */
2031        strcat(scanf_fmt, spec + 4);
2032
2033        return;
2034}
2035
2036char *shorten_unambiguous_ref(const char *refname, int strict)
2037{
2038        int i;
2039        static char **scanf_fmts;
2040        static int nr_rules;
2041        char *short_name;
2042
2043        /* pre generate scanf formats from ref_rev_parse_rules[] */
2044        if (!nr_rules) {
2045                size_t total_len = 0;
2046
2047                /* the rule list is NULL terminated, count them first */
2048                for (; ref_rev_parse_rules[nr_rules]; nr_rules++)
2049                        /* no +1 because strlen("%s") < strlen("%.*s") */
2050                        total_len += strlen(ref_rev_parse_rules[nr_rules]);
2051
2052                scanf_fmts = xmalloc(nr_rules * sizeof(char *) + total_len);
2053
2054                total_len = 0;
2055                for (i = 0; i < nr_rules; i++) {
2056                        scanf_fmts[i] = (char *)&scanf_fmts[nr_rules]
2057                                        + total_len;
2058                        gen_scanf_fmt(scanf_fmts[i], ref_rev_parse_rules[i]);
2059                        total_len += strlen(ref_rev_parse_rules[i]);
2060                }
2061        }
2062
2063        /* bail out if there are no rules */
2064        if (!nr_rules)
2065                return xstrdup(refname);
2066
2067        /* buffer for scanf result, at most refname must fit */
2068        short_name = xstrdup(refname);
2069
2070        /* skip first rule, it will always match */
2071        for (i = nr_rules - 1; i > 0 ; --i) {
2072                int j;
2073                int rules_to_fail = i;
2074                int short_name_len;
2075
2076                if (1 != sscanf(refname, scanf_fmts[i], short_name))
2077                        continue;
2078
2079                short_name_len = strlen(short_name);
2080
2081                /*
2082                 * in strict mode, all (except the matched one) rules
2083                 * must fail to resolve to a valid non-ambiguous ref
2084                 */
2085                if (strict)
2086                        rules_to_fail = nr_rules;
2087
2088                /*
2089                 * check if the short name resolves to a valid ref,
2090                 * but use only rules prior to the matched one
2091                 */
2092                for (j = 0; j < rules_to_fail; j++) {
2093                        const char *rule = ref_rev_parse_rules[j];
2094                        char refname[PATH_MAX];
2095
2096                        /* skip matched rule */
2097                        if (i == j)
2098                                continue;
2099
2100                        /*
2101                         * the short name is ambiguous, if it resolves
2102                         * (with this previous rule) to a valid ref
2103                         * read_ref() returns 0 on success
2104                         */
2105                        mksnpath(refname, sizeof(refname),
2106                                 rule, short_name_len, short_name);
2107                        if (ref_exists(refname))
2108                                break;
2109                }
2110
2111                /*
2112                 * short name is non-ambiguous if all previous rules
2113                 * haven't resolved to a valid ref
2114                 */
2115                if (j == rules_to_fail)
2116                        return short_name;
2117        }
2118
2119        free(short_name);
2120        return xstrdup(refname);
2121}