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

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "refs.h"
   4 #include "object-store.h"
   5 #include "commit.h"
   6 #include "tree-walk.h"
   7 #include "attr.h"
   8 #include "archive.h"
   9 #include "parse-options.h"
  10 #include "unpack-trees.h"
  11 #include "dir.h"
  12
  13 static char const * const archive_usage[] = {
  14         N_("git archive [<options>] <tree-ish> [<path>...]"),
  15         N_("git archive --list"),
  16         N_("git archive --remote <repo> [--exec <cmd>] [<options>] <tree-ish> [<path>...]"),
  17         N_("git archive --remote <repo> [--exec <cmd>] --list"),
  18         NULL
  19 };
  20
  21 static const struct archiver **archivers;
  22 static int nr_archivers;
  23 static int alloc_archivers;
  24 static int remote_allow_unreachable;
  25
  26 void register_archiver(struct archiver *ar)
  27 {
  28         ALLOC_GROW(archivers, nr_archivers + 1, alloc_archivers);
  29         archivers[nr_archivers++] = ar;
  30 }
  31
  32 void init_archivers(void)
  33 {
  34         init_tar_archiver();
  35         init_zip_archiver();
  36 }
  37
  38 static void format_subst(const struct commit *commit,
  39                          const char *src, size_t len,
  40                          struct strbuf *buf, struct pretty_print_context *ctx)
  41 {
  42         char *to_free = NULL;
  43         struct strbuf fmt = STRBUF_INIT;
  44
  45         if (src == buf->buf)
  46                 to_free = strbuf_detach(buf, NULL);
  47         for (;;) {
  48                 const char *b, *c;
  49
  50                 b = memmem(src, len, "$Format:", 8);
  51                 if (!b)
  52                         break;
  53                 c = memchr(b + 8, '$', (src + len) - b - 8);
  54                 if (!c)
  55                         break;
  56
  57                 strbuf_reset(&fmt);
  58                 strbuf_add(&fmt, b + 8, c - b - 8);
  59
  60                 strbuf_add(buf, src, b - src);
  61                 format_commit_message(commit, fmt.buf, buf, ctx);
  62                 len -= c + 1 - src;
  63                 src  = c + 1;
  64         }
  65         strbuf_add(buf, src, len);
  66         strbuf_release(&fmt);
  67         free(to_free);
  68 }
  69
  70 static void *object_file_to_archive(const struct archiver_args *args,
  71                                     const char *path,
  72                                     const struct object_id *oid,
  73                                     unsigned int mode,
  74                                     enum object_type *type,
  75                                     unsigned long *sizep)
  76 {
  77         void *buffer;
  78         const struct commit *commit = args->convert ? args->commit : NULL;
  79         struct checkout_metadata meta;
  80
  81         init_checkout_metadata(&meta, args->refname,
  82                                args->commit_oid ? args->commit_oid :
  83                                (args->tree ? &args->tree->object.oid : NULL), oid);
  84
  85         path += args->baselen;
  86         buffer = read_object_file(oid, type, sizep);
  87         if (buffer && S_ISREG(mode)) {
  88                 struct strbuf buf = STRBUF_INIT;
  89                 size_t size = 0;
  90
  91                 strbuf_attach(&buf, buffer, *sizep, *sizep + 1);
  92                 convert_to_working_tree(args->repo->index, path, buf.buf, buf.len, &buf, &meta);
  93                 if (commit)
  94                         format_subst(commit, buf.buf, buf.len, &buf, args->pretty_ctx);
  95                 buffer = strbuf_detach(&buf, &size);
  96                 *sizep = size;
  97         }
  98
  99         return buffer;
 100 }
 101
 102 struct directory {
 103         struct directory *up;
 104         struct object_id oid;
 105         int baselen, len;
 106         unsigned mode;
 107         char path[FLEX_ARRAY];
 108 };
 109
 110 struct archiver_context {
 111         struct archiver_args *args;
 112         write_archive_entry_fn_t write_entry;
 113         struct directory *bottom;
 114 };
 115
 116 static const struct attr_check *get_archive_attrs(struct index_state *istate,
 117                                                   const char *path)
 118 {
 119         static struct attr_check *check;
 120         if (!check)
 121                 check = attr_check_initl("export-ignore", "export-subst", NULL);
 122         git_check_attr(istate, path, check);
 123         return check;
 124 }
 125
 126 static int check_attr_export_ignore(const struct attr_check *check)
 127 {
 128         return check && ATTR_TRUE(check->items[0].value);
 129 }
 130
 131 static int check_attr_export_subst(const struct attr_check *check)
 132 {
 133         return check && ATTR_TRUE(check->items[1].value);
 134 }
 135
 136 static int write_archive_entry(const struct object_id *oid, const char *base,
 137                 int baselen, const char *filename, unsigned mode,
 138                 void *context)
 139 {
 140         static struct strbuf path = STRBUF_INIT;
 141         struct archiver_context *c = context;
 142         struct archiver_args *args = c->args;
 143         write_archive_entry_fn_t write_entry = c->write_entry;
 144         int err;
 145         const char *path_without_prefix;
 146         unsigned long size;
 147         void *buffer;
 148         enum object_type type;
 149
 150         args->convert = 0;
 151         strbuf_reset(&path);
 152         strbuf_grow(&path, PATH_MAX);
 153         strbuf_add(&path, args->base, args->baselen);
 154         strbuf_add(&path, base, baselen);
 155         strbuf_addstr(&path, filename);
 156         if (S_ISDIR(mode) || S_ISGITLINK(mode))
 157                 strbuf_addch(&path, '/');
 158         path_without_prefix = path.buf + args->baselen;
 159
 160         if (!S_ISDIR(mode)) {
 161                 const struct attr_check *check;
 162                 check = get_archive_attrs(args->repo->index, path_without_prefix);
 163                 if (check_attr_export_ignore(check))
 164                         return 0;
 165                 args->convert = check_attr_export_subst(check);
 166         }
 167
 168         if (S_ISDIR(mode) || S_ISGITLINK(mode)) {
 169                 if (args->verbose)
 170                         fprintf(stderr, "%.*s\n", (int)path.len, path.buf);
 171                 err = write_entry(args, oid, path.buf, path.len, mode, NULL, 0);
 172                 if (err)
 173                         return err;
 174                 return (S_ISDIR(mode) ? READ_TREE_RECURSIVE : 0);
 175         }
 176
 177         if (args->verbose)
 178                 fprintf(stderr, "%.*s\n", (int)path.len, path.buf);
 179
 180         /* Stream it? */
 181         if (S_ISREG(mode) && !args->convert &&
 182             oid_object_info(args->repo, oid, &size) == OBJ_BLOB &&
 183             size > big_file_threshold)
 184                 return write_entry(args, oid, path.buf, path.len, mode, NULL, size);
 185
 186         buffer = object_file_to_archive(args, path.buf, oid, mode, &type, &size);
 187         if (!buffer)
 188                 return error(_("cannot read %s"), oid_to_hex(oid));
 189         err = write_entry(args, oid, path.buf, path.len, mode, buffer, size);
 190         free(buffer);
 191         return err;
 192 }
 193
 194 static void queue_directory(const unsigned char *sha1,
 195                 struct strbuf *base, const char *filename,
 196                 unsigned mode, struct archiver_context *c)
 197 {
 198         struct directory *d;
 199         size_t len = st_add4(base->len, 1, strlen(filename), 1);
 200         d = xmalloc(st_add(sizeof(*d), len));
 201         d->up      = c->bottom;
 202         d->baselen = base->len;
 203         d->mode    = mode;
 204         c->bottom  = d;
 205         d->len = xsnprintf(d->path, len, "%.*s%s/", (int)base->len, base->buf, filename);
 206         oidread(&d->oid, sha1);
 207 }
 208
 209 static int write_directory(struct archiver_context *c)
 210 {
 211         struct directory *d = c->bottom;
 212         int ret;
 213
 214         if (!d)
 215                 return 0;
 216         c->bottom = d->up;
 217         d->path[d->len - 1] = '\0'; /* no trailing slash */
 218         ret =
 219                 write_directory(c) ||
 220                 write_archive_entry(&d->oid, d->path, d->baselen,
 221                                     d->path + d->baselen, d->mode,
 222                                     c) != READ_TREE_RECURSIVE;
 223         free(d);
 224         return ret ? -1 : 0;
 225 }
 226
 227 static int queue_or_write_archive_entry(const struct object_id *oid,
 228                 struct strbuf *base, const char *filename,
 229                 unsigned mode, void *context)
 230 {
 231         struct archiver_context *c = context;
 232
 233         while (c->bottom &&
 234                !(base->len >= c->bottom->len &&
 235                  !strncmp(base->buf, c->bottom->path, c->bottom->len))) {
 236                 struct directory *next = c->bottom->up;
 237                 free(c->bottom);
 238                 c->bottom = next;
 239         }
 240
 241         if (S_ISDIR(mode)) {
 242                 size_t baselen = base->len;
 243                 const struct attr_check *check;
 244
 245                 /* Borrow base, but restore its original value when done. */
 246                 strbuf_addstr(base, filename);
 247                 strbuf_addch(base, '/');
 248                 check = get_archive_attrs(c->args->repo->index, base->buf);
 249                 strbuf_setlen(base, baselen);
 250
 251                 if (check_attr_export_ignore(check))
 252                         return 0;
 253                 queue_directory(oid->hash, base, filename,
 254                                 mode, c);
 255                 return READ_TREE_RECURSIVE;
 256         }
 257
 258         if (write_directory(c))
 259                 return -1;
 260         return write_archive_entry(oid, base->buf, base->len, filename, mode,
 261                                    context);
 262 }
 263
 264 struct extra_file_info {
 265         char *base;
 266         struct stat stat;
 267 };
 268
 269 int write_archive_entries(struct archiver_args *args,
 270                 write_archive_entry_fn_t write_entry)
 271 {
 272         struct archiver_context context;
 273         struct unpack_trees_options opts;
 274         struct tree_desc t;
 275         int err;
 276         struct strbuf path_in_archive = STRBUF_INIT;
 277         struct strbuf content = STRBUF_INIT;
 278         struct object_id fake_oid;
 279         int i;
 280
 281         oidcpy(&fake_oid, null_oid());
 282
 283         if (args->baselen > 0 && args->base[args->baselen - 1] == '/') {
 284                 size_t len = args->baselen;
 285
 286                 while (len > 1 && args->base[len - 2] == '/')
 287                         len--;
 288                 if (args->verbose)
 289                         fprintf(stderr, "%.*s\n", (int)len, args->base);
 290                 err = write_entry(args, &args->tree->object.oid, args->base,
 291                                   len, 040777, NULL, 0);
 292                 if (err)
 293                         return err;
 294         }
 295
 296         memset(&context, 0, sizeof(context));
 297         context.args = args;
 298         context.write_entry = write_entry;
 299
 300         /*
 301          * Setup index and instruct attr to read index only
 302          */
 303         if (!args->worktree_attributes) {
 304                 memset(&opts, 0, sizeof(opts));
 305                 opts.index_only = 1;
 306                 opts.head_idx = -1;
 307                 opts.src_index = args->repo->index;
 308                 opts.dst_index = args->repo->index;
 309                 opts.fn = oneway_merge;
 310                 init_tree_desc(&t, args->tree->buffer, args->tree->size);
 311                 if (unpack_trees(1, &t, &opts))
 312                         return -1;
 313                 git_attr_set_direction(GIT_ATTR_INDEX);
 314         }
 315
 316         err = read_tree(args->repo, args->tree,
 317                         &args->pathspec,
 318                         queue_or_write_archive_entry,
 319                         &context);
 320         if (err == READ_TREE_RECURSIVE)
 321                 err = 0;
 322         while (context.bottom) {
 323                 struct directory *next = context.bottom->up;
 324                 free(context.bottom);
 325                 context.bottom = next;
 326         }
 327
 328         for (i = 0; i < args->extra_files.nr; i++) {
 329                 struct string_list_item *item = args->extra_files.items + i;
 330                 char *path = item->string;
 331                 struct extra_file_info *info = item->util;
 332
 333                 put_be64(fake_oid.hash, i + 1);
 334
 335                 strbuf_reset(&path_in_archive);
 336                 if (info->base)
 337                         strbuf_addstr(&path_in_archive, info->base);
 338                 strbuf_addstr(&path_in_archive, basename(path));
 339
 340                 strbuf_reset(&content);
 341                 if (strbuf_read_file(&content, path, info->stat.st_size) < 0)
 342                         err = error_errno(_("could not read '%s'"), path);
 343                 else
 344                         err = write_entry(args, &fake_oid, path_in_archive.buf,
 345                                           path_in_archive.len,
 346                                           info->stat.st_mode,
 347                                           content.buf, content.len);
 348                 if (err)
 349                         break;
 350         }
 351         strbuf_release(&path_in_archive);
 352         strbuf_release(&content);
 353
 354         return err;
 355 }
 356
 357 static const struct archiver *lookup_archiver(const char *name)
 358 {
 359         int i;
 360
 361         if (!name)
 362                 return NULL;
 363
 364         for (i = 0; i < nr_archivers; i++) {
 365                 if (!strcmp(name, archivers[i]->name))
 366                         return archivers[i];
 367         }
 368         return NULL;
 369 }
 370
 371 struct path_exists_context {
 372         struct pathspec pathspec;
 373         struct archiver_args *args;
 374 };
 375
 376 static int reject_entry(const struct object_id *oid, struct strbuf *base,
 377                         const char *filename, unsigned mode,
 378                         void *context)
 379 {
 380         int ret = -1;
 381         struct path_exists_context *ctx = context;
 382
 383         if (S_ISDIR(mode)) {
 384                 struct strbuf sb = STRBUF_INIT;
 385                 strbuf_addbuf(&sb, base);
 386                 strbuf_addstr(&sb, filename);
 387                 if (!match_pathspec(ctx->args->repo->index,
 388                                     &ctx->pathspec,
 389                                     sb.buf, sb.len, 0, NULL, 1))
 390                         ret = READ_TREE_RECURSIVE;
 391                 strbuf_release(&sb);
 392         }
 393         return ret;
 394 }
 395
 396 static int path_exists(struct archiver_args *args, const char *path)
 397 {
 398         const char *paths[] = { path, NULL };
 399         struct path_exists_context ctx;
 400         int ret;
 401
 402         ctx.args = args;
 403         parse_pathspec(&ctx.pathspec, 0, 0, "", paths);
 404         ctx.pathspec.recursive = 1;
 405         ret = read_tree(args->repo, args->tree,
 406                         &ctx.pathspec,
 407                         reject_entry, &ctx);
 408         clear_pathspec(&ctx.pathspec);
 409         return ret != 0;
 410 }
 411
 412 static void parse_pathspec_arg(const char **pathspec,
 413                 struct archiver_args *ar_args)
 414 {
 415         /*
 416          * must be consistent with parse_pathspec in path_exists()
 417          * Also if pathspec patterns are dependent, we're in big
 418          * trouble as we test each one separately
 419          */
 420         parse_pathspec(&ar_args->pathspec, 0,
 421                        PATHSPEC_PREFER_FULL,
 422                        "", pathspec);
 423         ar_args->pathspec.recursive = 1;
 424         if (pathspec) {
 425                 while (*pathspec) {
 426                         if (**pathspec && !path_exists(ar_args, *pathspec))
 427                                 die(_("pathspec '%s' did not match any files"), *pathspec);
 428                         pathspec++;
 429                 }
 430         }
 431 }
 432
 433 static void parse_treeish_arg(const char **argv,
 434                 struct archiver_args *ar_args, const char *prefix,
 435                 int remote)
 436 {
 437         const char *name = argv[0];
 438         const struct object_id *commit_oid;
 439         time_t archive_time;
 440         struct tree *tree;
 441         const struct commit *commit;
 442         struct object_id oid;
 443         char *ref = NULL;
 444
 445         /* Remotes are only allowed to fetch actual refs */
 446         if (remote && !remote_allow_unreachable) {
 447                 const char *colon = strchrnul(name, ':');
 448                 int refnamelen = colon - name;
 449
 450                 if (!dwim_ref(name, refnamelen, &oid, &ref, 0))
 451                         die(_("no such ref: %.*s"), refnamelen, name);
 452         } else {
 453                 dwim_ref(name, strlen(name), &oid, &ref, 0);
 454         }
 455
 456         if (get_oid(name, &oid))
 457                 die(_("not a valid object name: %s"), name);
 458
 459         commit = lookup_commit_reference_gently(ar_args->repo, &oid, 1);
 460         if (commit) {
 461                 commit_oid = &commit->object.oid;
 462                 archive_time = commit->date;
 463         } else {
 464                 commit_oid = NULL;
 465                 archive_time = time(NULL);
 466         }
 467
 468         tree = parse_tree_indirect(&oid);
 469         if (tree == NULL)
 470                 die(_("not a tree object: %s"), oid_to_hex(&oid));
 471
 472         if (prefix) {
 473                 struct object_id tree_oid;
 474                 unsigned short mode;
 475                 int err;
 476
 477                 err = get_tree_entry(ar_args->repo,
 478                                      &tree->object.oid,
 479                                      prefix, &tree_oid,
 480                                      &mode);
 481                 if (err || !S_ISDIR(mode))
 482                         die(_("current working directory is untracked"));
 483
 484                 tree = parse_tree_indirect(&tree_oid);
 485         }
 486         ar_args->refname = ref;
 487         ar_args->tree = tree;
 488         ar_args->commit_oid = commit_oid;
 489         ar_args->commit = commit;
 490         ar_args->time = archive_time;
 491 }
 492
 493 static void extra_file_info_clear(void *util, const char *str)
 494 {
 495         struct extra_file_info *info = util;
 496         free(info->base);
 497         free(info);
 498 }
 499
 500 static int add_file_cb(const struct option *opt, const char *arg, int unset)
 501 {
 502         struct archiver_args *args = opt->value;
 503         const char **basep = (const char **)opt->defval;
 504         const char *base = *basep;
 505         char *path;
 506         struct string_list_item *item;
 507         struct extra_file_info *info;
 508
 509         if (unset) {
 510                 string_list_clear_func(&args->extra_files,
 511                                        extra_file_info_clear);
 512                 return 0;
 513         }
 514
 515         if (!arg)
 516                 return -1;
 517
 518         path = prefix_filename(args->prefix, arg);
 519         item = string_list_append_nodup(&args->extra_files, path);
 520         item->util = info = xmalloc(sizeof(*info));
 521         info->base = xstrdup_or_null(base);
 522         if (stat(path, &info->stat))
 523                 die(_("File not found: %s"), path);
 524         if (!S_ISREG(info->stat.st_mode))
 525                 die(_("Not a regular file: %s"), path);
 526         return 0;
 527 }
 528
 529 static int number_callback(const struct option *opt, const char *arg, int unset)
 530 {
 531         BUG_ON_OPT_NEG(unset);
 532         *(int *)opt->value = strtol(arg, NULL, 10);
 533         return 0;
 534 }
 535
 536 static int parse_archive_args(int argc, const char **argv,
 537                 const struct archiver **ar, struct archiver_args *args,
 538                 const char *name_hint, int is_remote)
 539 {
 540         const char *format = NULL;
 541         const char *base = NULL;
 542         const char *remote = NULL;
 543         const char *exec = NULL;
 544         const char *output = NULL;
 545         int compression_level = -1;
 546         int verbose = 0;
 547         int i;
 548         int list = 0;
 549         int worktree_attributes = 0;
 550         struct option opts[] = {
 551                 OPT_GROUP(""),
 552                 OPT_STRING(0, "format", &format, N_("fmt"), N_("archive format")),
 553                 OPT_STRING(0, "prefix", &base, N_("prefix"),
 554                         N_("prepend prefix to each pathname in the archive")),
 555                 { OPTION_CALLBACK, 0, "add-file", args, N_("file"),
 556                   N_("add untracked file to archive"), 0, add_file_cb,
 557                   (intptr_t)&base },
 558                 OPT_STRING('o', "output", &output, N_("file"),
 559                         N_("write the archive to this file")),
 560                 OPT_BOOL(0, "worktree-attributes", &worktree_attributes,
 561                         N_("read .gitattributes in working directory")),
 562                 OPT__VERBOSE(&verbose, N_("report archived files on stderr")),
 563                 OPT_NUMBER_CALLBACK(&compression_level,
 564                         N_("set compression level"), number_callback),
 565                 OPT_GROUP(""),
 566                 OPT_BOOL('l', "list", &list,
 567                         N_("list supported archive formats")),
 568                 OPT_GROUP(""),
 569                 OPT_STRING(0, "remote", &remote, N_("repo"),
 570                         N_("retrieve the archive from remote repository <repo>")),
 571                 OPT_STRING(0, "exec", &exec, N_("command"),
 572                         N_("path to the remote git-upload-archive command")),
 573                 OPT_END()
 574         };
 575
 576         argc = parse_options(argc, argv, NULL, opts, archive_usage, 0);
 577
 578         if (remote)
 579                 die(_("Unexpected option --remote"));
 580         if (exec)
 581                 die(_("Option --exec can only be used together with --remote"));
 582         if (output)
 583                 die(_("Unexpected option --output"));
 584         if (is_remote && args->extra_files.nr)
 585                 die(_("Options --add-file and --remote cannot be used together"));
 586
 587         if (!base)
 588                 base = "";
 589
 590         if (list) {
 591                 for (i = 0; i < nr_archivers; i++)
 592                         if (!is_remote || archivers[i]->flags & ARCHIVER_REMOTE)
 593                                 printf("%s\n", archivers[i]->name);
 594                 exit(0);
 595         }
 596
 597         if (!format && name_hint)
 598                 format = archive_format_from_filename(name_hint);
 599         if (!format)
 600                 format = "tar";
 601
 602         /* We need at least one parameter -- tree-ish */
 603         if (argc < 1)
 604                 usage_with_options(archive_usage, opts);
 605         *ar = lookup_archiver(format);
 606         if (!*ar || (is_remote && !((*ar)->flags & ARCHIVER_REMOTE)))
 607                 die(_("Unknown archive format '%s'"), format);
 608
 609         args->compression_level = Z_DEFAULT_COMPRESSION;
 610         if (compression_level != -1) {
 611                 int levels_ok = (*ar)->flags & ARCHIVER_WANT_COMPRESSION_LEVELS;
 612                 int high_ok = (*ar)->flags & ARCHIVER_HIGH_COMPRESSION_LEVELS;
 613                 if (levels_ok && (compression_level <= 9 || high_ok))
 614                         args->compression_level = compression_level;
 615                 else {
 616                         die(_("Argument not supported for format '%s': -%d"),
 617                                         format, compression_level);
 618                 }
 619         }
 620         args->verbose = verbose;
 621         args->base = base;
 622         args->baselen = strlen(base);
 623         args->worktree_attributes = worktree_attributes;
 624
 625         return argc;
 626 }
 627
 628 int write_archive(int argc, const char **argv, const char *prefix,
 629                   struct repository *repo,
 630                   const char *name_hint, int remote)
 631 {
 632         const struct archiver *ar = NULL;
 633         struct pretty_print_describe_status describe_status = {0};
 634         struct pretty_print_context ctx = {0};
 635         struct archiver_args args;
 636         int rc;
 637
 638         git_config_get_bool("uploadarchive.allowunreachable", &remote_allow_unreachable);
 639         git_config(git_default_config, NULL);
 640
 641         describe_status.max_invocations = 1;
 642         ctx.date_mode.type = DATE_NORMAL;
 643         ctx.abbrev = DEFAULT_ABBREV;
 644         ctx.describe_status = &describe_status;
 645         args.pretty_ctx = &ctx;
 646         args.repo = repo;
 647         args.prefix = prefix;
 648         string_list_init(&args.extra_files, 1);
 649         argc = parse_archive_args(argc, argv, &ar, &args, name_hint, remote);
 650         if (!startup_info->have_repository) {
 651                 /*
 652                  * We know this will die() with an error, so we could just
 653                  * die ourselves; but its error message will be more specific
 654                  * than what we could write here.
 655                  */
 656                 setup_git_directory();
 657         }
 658
 659         parse_treeish_arg(argv, &args, prefix, remote);
 660         parse_pathspec_arg(argv + 1, &args);
 661
 662         rc = ar->write_archive(ar, &args);
 663
 664         string_list_clear_func(&args.extra_files, extra_file_info_clear);
 665         free(args.refname);
 666
 667         return rc;
 668 }
 669
 670 static int match_extension(const char *filename, const char *ext)
 671 {
 672         int prefixlen = strlen(filename) - strlen(ext);
 673
 674         /*
 675          * We need 1 character for the '.', and 1 character to ensure that the
 676          * prefix is non-empty (k.e., we don't match .tar.gz with no actual
 677          * filename).
 678          */
 679         if (prefixlen < 2 || filename[prefixlen - 1] != '.')
 680                 return 0;
 681         return !strcmp(filename + prefixlen, ext);
 682 }
 683
 684 const char *archive_format_from_filename(const char *filename)
 685 {
 686         int i;
 687
 688         for (i = 0; i < nr_archivers; i++)
 689                 if (match_extension(filename, archivers[i]->name))
 690                         return archivers[i]->name;
 691         return NULL;
 692 }