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         hashcpy(d->oid.hash, 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 = null_oid;
 279         int i;
 280
 281         if (args->baselen > 0 && args->base[args->baselen - 1] == '/') {
 282                 size_t len = args->baselen;
 283
 284                 while (len > 1 && args->base[len - 2] == '/')
 285                         len--;
 286                 if (args->verbose)
 287                         fprintf(stderr, "%.*s\n", (int)len, args->base);
 288                 err = write_entry(args, &args->tree->object.oid, args->base,
 289                                   len, 040777, NULL, 0);
 290                 if (err)
 291                         return err;
 292         }
 293
 294         memset(&context, 0, sizeof(context));
 295         context.args = args;
 296         context.write_entry = write_entry;
 297
 298         /*
 299          * Setup index and instruct attr to read index only
 300          */
 301         if (!args->worktree_attributes) {
 302                 memset(&opts, 0, sizeof(opts));
 303                 opts.index_only = 1;
 304                 opts.head_idx = -1;
 305                 opts.src_index = args->repo->index;
 306                 opts.dst_index = args->repo->index;
 307                 opts.fn = oneway_merge;
 308                 init_tree_desc(&t, args->tree->buffer, args->tree->size);
 309                 if (unpack_trees(1, &t, &opts))
 310                         return -1;
 311                 git_attr_set_direction(GIT_ATTR_INDEX);
 312         }
 313
 314         err = read_tree(args->repo, args->tree,
 315                         &args->pathspec,
 316                         queue_or_write_archive_entry,
 317                         &context);
 318         if (err == READ_TREE_RECURSIVE)
 319                 err = 0;
 320         while (context.bottom) {
 321                 struct directory *next = context.bottom->up;
 322                 free(context.bottom);
 323                 context.bottom = next;
 324         }
 325
 326         for (i = 0; i < args->extra_files.nr; i++) {
 327                 struct string_list_item *item = args->extra_files.items + i;
 328                 char *path = item->string;
 329                 struct extra_file_info *info = item->util;
 330
 331                 put_be64(fake_oid.hash, i + 1);
 332
 333                 strbuf_reset(&path_in_archive);
 334                 if (info->base)
 335                         strbuf_addstr(&path_in_archive, info->base);
 336                 strbuf_addstr(&path_in_archive, basename(path));
 337
 338                 strbuf_reset(&content);
 339                 if (strbuf_read_file(&content, path, info->stat.st_size) < 0)
 340                         err = error_errno(_("could not read '%s'"), path);
 341                 else
 342                         err = write_entry(args, &fake_oid, path_in_archive.buf,
 343                                           path_in_archive.len,
 344                                           info->stat.st_mode,
 345                                           content.buf, content.len);
 346                 if (err)
 347                         break;
 348         }
 349         strbuf_release(&path_in_archive);
 350         strbuf_release(&content);
 351
 352         return err;
 353 }
 354
 355 static const struct archiver *lookup_archiver(const char *name)
 356 {
 357         int i;
 358
 359         if (!name)
 360                 return NULL;
 361
 362         for (i = 0; i < nr_archivers; i++) {
 363                 if (!strcmp(name, archivers[i]->name))
 364                         return archivers[i];
 365         }
 366         return NULL;
 367 }
 368
 369 struct path_exists_context {
 370         struct pathspec pathspec;
 371         struct archiver_args *args;
 372 };
 373
 374 static int reject_entry(const struct object_id *oid, struct strbuf *base,
 375                         const char *filename, unsigned mode,
 376                         void *context)
 377 {
 378         int ret = -1;
 379         struct path_exists_context *ctx = context;
 380
 381         if (S_ISDIR(mode)) {
 382                 struct strbuf sb = STRBUF_INIT;
 383                 strbuf_addbuf(&sb, base);
 384                 strbuf_addstr(&sb, filename);
 385                 if (!match_pathspec(ctx->args->repo->index,
 386                                     &ctx->pathspec,
 387                                     sb.buf, sb.len, 0, NULL, 1))
 388                         ret = READ_TREE_RECURSIVE;
 389                 strbuf_release(&sb);
 390         }
 391         return ret;
 392 }
 393
 394 static int path_exists(struct archiver_args *args, const char *path)
 395 {
 396         const char *paths[] = { path, NULL };
 397         struct path_exists_context ctx;
 398         int ret;
 399
 400         ctx.args = args;
 401         parse_pathspec(&ctx.pathspec, 0, 0, "", paths);
 402         ctx.pathspec.recursive = 1;
 403         ret = read_tree(args->repo, args->tree,
 404                         &ctx.pathspec,
 405                         reject_entry, &ctx);
 406         clear_pathspec(&ctx.pathspec);
 407         return ret != 0;
 408 }
 409
 410 static void parse_pathspec_arg(const char **pathspec,
 411                 struct archiver_args *ar_args)
 412 {
 413         /*
 414          * must be consistent with parse_pathspec in path_exists()
 415          * Also if pathspec patterns are dependent, we're in big
 416          * trouble as we test each one separately
 417          */
 418         parse_pathspec(&ar_args->pathspec, 0,
 419                        PATHSPEC_PREFER_FULL,
 420                        "", pathspec);
 421         ar_args->pathspec.recursive = 1;
 422         if (pathspec) {
 423                 while (*pathspec) {
 424                         if (**pathspec && !path_exists(ar_args, *pathspec))
 425                                 die(_("pathspec '%s' did not match any files"), *pathspec);
 426                         pathspec++;
 427                 }
 428         }
 429 }
 430
 431 static void parse_treeish_arg(const char **argv,
 432                 struct archiver_args *ar_args, const char *prefix,
 433                 int remote)
 434 {
 435         const char *name = argv[0];
 436         const struct object_id *commit_oid;
 437         time_t archive_time;
 438         struct tree *tree;
 439         const struct commit *commit;
 440         struct object_id oid;
 441         char *ref = NULL;
 442
 443         /* Remotes are only allowed to fetch actual refs */
 444         if (remote && !remote_allow_unreachable) {
 445                 const char *colon = strchrnul(name, ':');
 446                 int refnamelen = colon - name;
 447
 448                 if (!dwim_ref(name, refnamelen, &oid, &ref, 0))
 449                         die(_("no such ref: %.*s"), refnamelen, name);
 450         } else {
 451                 dwim_ref(name, strlen(name), &oid, &ref, 0);
 452         }
 453
 454         if (get_oid(name, &oid))
 455                 die(_("not a valid object name: %s"), name);
 456
 457         commit = lookup_commit_reference_gently(ar_args->repo, &oid, 1);
 458         if (commit) {
 459                 commit_oid = &commit->object.oid;
 460                 archive_time = commit->date;
 461         } else {
 462                 commit_oid = NULL;
 463                 archive_time = time(NULL);
 464         }
 465
 466         tree = parse_tree_indirect(&oid);
 467         if (tree == NULL)
 468                 die(_("not a tree object: %s"), oid_to_hex(&oid));
 469
 470         if (prefix) {
 471                 struct object_id tree_oid;
 472                 unsigned short mode;
 473                 int err;
 474
 475                 err = get_tree_entry(ar_args->repo,
 476                                      &tree->object.oid,
 477                                      prefix, &tree_oid,
 478                                      &mode);
 479                 if (err || !S_ISDIR(mode))
 480                         die(_("current working directory is untracked"));
 481
 482                 tree = parse_tree_indirect(&tree_oid);
 483         }
 484         ar_args->refname = ref;
 485         ar_args->tree = tree;
 486         ar_args->commit_oid = commit_oid;
 487         ar_args->commit = commit;
 488         ar_args->time = archive_time;
 489 }
 490
 491 static void extra_file_info_clear(void *util, const char *str)
 492 {
 493         struct extra_file_info *info = util;
 494         free(info->base);
 495         free(info);
 496 }
 497
 498 static int add_file_cb(const struct option *opt, const char *arg, int unset)
 499 {
 500         struct archiver_args *args = opt->value;
 501         const char **basep = (const char **)opt->defval;
 502         const char *base = *basep;
 503         char *path;
 504         struct string_list_item *item;
 505         struct extra_file_info *info;
 506
 507         if (unset) {
 508                 string_list_clear_func(&args->extra_files,
 509                                        extra_file_info_clear);
 510                 return 0;
 511         }
 512
 513         if (!arg)
 514                 return -1;
 515
 516         path = prefix_filename(args->prefix, arg);
 517         item = string_list_append_nodup(&args->extra_files, path);
 518         item->util = info = xmalloc(sizeof(*info));
 519         info->base = xstrdup_or_null(base);
 520         if (stat(path, &info->stat))
 521                 die(_("File not found: %s"), path);
 522         if (!S_ISREG(info->stat.st_mode))
 523                 die(_("Not a regular file: %s"), path);
 524         return 0;
 525 }
 526
 527 static int number_callback(const struct option *opt, const char *arg, int unset)
 528 {
 529         BUG_ON_OPT_NEG(unset);
 530         *(int *)opt->value = strtol(arg, NULL, 10);
 531         return 0;
 532 }
 533
 534 static int parse_archive_args(int argc, const char **argv,
 535                 const struct archiver **ar, struct archiver_args *args,
 536                 const char *name_hint, int is_remote)
 537 {
 538         const char *format = NULL;
 539         const char *base = NULL;
 540         const char *remote = NULL;
 541         const char *exec = NULL;
 542         const char *output = NULL;
 543         int compression_level = -1;
 544         int verbose = 0;
 545         int i;
 546         int list = 0;
 547         int worktree_attributes = 0;
 548         struct option opts[] = {
 549                 OPT_GROUP(""),
 550                 OPT_STRING(0, "format", &format, N_("fmt"), N_("archive format")),
 551                 OPT_STRING(0, "prefix", &base, N_("prefix"),
 552                         N_("prepend prefix to each pathname in the archive")),
 553                 { OPTION_CALLBACK, 0, "add-file", args, N_("file"),
 554                   N_("add untracked file to archive"), 0, add_file_cb,
 555                   (intptr_t)&base },
 556                 OPT_STRING('o', "output", &output, N_("file"),
 557                         N_("write the archive to this file")),
 558                 OPT_BOOL(0, "worktree-attributes", &worktree_attributes,
 559                         N_("read .gitattributes in working directory")),
 560                 OPT__VERBOSE(&verbose, N_("report archived files on stderr")),
 561                 OPT_NUMBER_CALLBACK(&compression_level,
 562                         N_("set compression level"), number_callback),
 563                 OPT_GROUP(""),
 564                 OPT_BOOL('l', "list", &list,
 565                         N_("list supported archive formats")),
 566                 OPT_GROUP(""),
 567                 OPT_STRING(0, "remote", &remote, N_("repo"),
 568                         N_("retrieve the archive from remote repository <repo>")),
 569                 OPT_STRING(0, "exec", &exec, N_("command"),
 570                         N_("path to the remote git-upload-archive command")),
 571                 OPT_END()
 572         };
 573
 574         argc = parse_options(argc, argv, NULL, opts, archive_usage, 0);
 575
 576         if (remote)
 577                 die(_("Unexpected option --remote"));
 578         if (exec)
 579                 die(_("Option --exec can only be used together with --remote"));
 580         if (output)
 581                 die(_("Unexpected option --output"));
 582         if (is_remote && args->extra_files.nr)
 583                 die(_("Options --add-file and --remote cannot be used together"));
 584
 585         if (!base)
 586                 base = "";
 587
 588         if (list) {
 589                 for (i = 0; i < nr_archivers; i++)
 590                         if (!is_remote || archivers[i]->flags & ARCHIVER_REMOTE)
 591                                 printf("%s\n", archivers[i]->name);
 592                 exit(0);
 593         }
 594
 595         if (!format && name_hint)
 596                 format = archive_format_from_filename(name_hint);
 597         if (!format)
 598                 format = "tar";
 599
 600         /* We need at least one parameter -- tree-ish */
 601         if (argc < 1)
 602                 usage_with_options(archive_usage, opts);
 603         *ar = lookup_archiver(format);
 604         if (!*ar || (is_remote && !((*ar)->flags & ARCHIVER_REMOTE)))
 605                 die(_("Unknown archive format '%s'"), format);
 606
 607         args->compression_level = Z_DEFAULT_COMPRESSION;
 608         if (compression_level != -1) {
 609                 int levels_ok = (*ar)->flags & ARCHIVER_WANT_COMPRESSION_LEVELS;
 610                 int high_ok = (*ar)->flags & ARCHIVER_HIGH_COMPRESSION_LEVELS;
 611                 if (levels_ok && (compression_level <= 9 || high_ok))
 612                         args->compression_level = compression_level;
 613                 else {
 614                         die(_("Argument not supported for format '%s': -%d"),
 615                                         format, compression_level);
 616                 }
 617         }
 618         args->verbose = verbose;
 619         args->base = base;
 620         args->baselen = strlen(base);
 621         args->worktree_attributes = worktree_attributes;
 622
 623         return argc;
 624 }
 625
 626 int write_archive(int argc, const char **argv, const char *prefix,
 627                   struct repository *repo,
 628                   const char *name_hint, int remote)
 629 {
 630         const struct archiver *ar = NULL;
 631         struct pretty_print_describe_status describe_status = {0};
 632         struct pretty_print_context ctx = {0};
 633         struct archiver_args args;
 634         int rc;
 635
 636         git_config_get_bool("uploadarchive.allowunreachable", &remote_allow_unreachable);
 637         git_config(git_default_config, NULL);
 638
 639         describe_status.max_invocations = 1;
 640         ctx.date_mode.type = DATE_NORMAL;
 641         ctx.abbrev = DEFAULT_ABBREV;
 642         ctx.describe_status = &describe_status;
 643         args.pretty_ctx = &ctx;
 644         args.repo = repo;
 645         args.prefix = prefix;
 646         string_list_init(&args.extra_files, 1);
 647         argc = parse_archive_args(argc, argv, &ar, &args, name_hint, remote);
 648         if (!startup_info->have_repository) {
 649                 /*
 650                  * We know this will die() with an error, so we could just
 651                  * die ourselves; but its error message will be more specific
 652                  * than what we could write here.
 653                  */
 654                 setup_git_directory();
 655         }
 656
 657         parse_treeish_arg(argv, &args, prefix, remote);
 658         parse_pathspec_arg(argv + 1, &args);
 659
 660         rc = ar->write_archive(ar, &args);
 661
 662         string_list_clear_func(&args.extra_files, extra_file_info_clear);
 663         free(args.refname);
 664
 665         return rc;
 666 }
 667
 668 static int match_extension(const char *filename, const char *ext)
 669 {
 670         int prefixlen = strlen(filename) - strlen(ext);
 671
 672         /*
 673          * We need 1 character for the '.', and 1 character to ensure that the
 674          * prefix is non-empty (k.e., we don't match .tar.gz with no actual
 675          * filename).
 676          */
 677         if (prefixlen < 2 || filename[prefixlen - 1] != '.')
 678                 return 0;
 679         return !strcmp(filename + prefixlen, ext);
 680 }
 681
 682 const char *archive_format_from_filename(const char *filename)
 683 {
 684         int i;
 685
 686         for (i = 0; i < nr_archivers; i++)
 687                 if (match_extension(filename, archivers[i]->name))
 688                         return archivers[i]->name;
 689         return NULL;
 690 }