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