connect.c

   1 #include "git-compat-util.h"
   2 #include "cache.h"
   3 #include "pkt-line.h"
   4 #include "quote.h"
   5 #include "refs.h"
   6 #include "run-command.h"
   7
   8 static char *server_capabilities;
   9
  10 static int check_ref(const char *name, int len, unsigned int flags)
  11 {
  12         if (!flags)
  13                 return 1;
  14
  15         if (len < 5 || memcmp(name, "refs/", 5))
  16                 return 0;
  17
  18         /* Skip the "refs/" part */
  19         name += 5;
  20         len -= 5;
  21
  22         /* REF_NORMAL means that we don't want the magic fake tag refs */
  23         if ((flags & REF_NORMAL) && check_ref_format(name) < 0)
  24                 return 0;
  25
  26         /* REF_HEADS means that we want regular branch heads */
  27         if ((flags & REF_HEADS) && !memcmp(name, "heads/", 6))
  28                 return 1;
  29
  30         /* REF_TAGS means that we want tags */
  31         if ((flags & REF_TAGS) && !memcmp(name, "tags/", 5))
  32                 return 1;
  33
  34         /* All type bits clear means that we are ok with anything */
  35         return !(flags & ~REF_NORMAL);
  36 }
  37
  38 /*
  39  * Read all the refs from the other end
  40  */
  41 struct ref **get_remote_heads(int in, struct ref **list,
  42                               int nr_match, char **match,
  43                               unsigned int flags)
  44 {
  45         *list = NULL;
  46         for (;;) {
  47                 struct ref *ref;
  48                 unsigned char old_sha1[20];
  49                 static char buffer[1000];
  50                 char *name;
  51                 int len, name_len;
  52
  53                 len = packet_read_line(in, buffer, sizeof(buffer));
  54                 if (!len)
  55                         break;
  56                 if (buffer[len-1] == '\n')
  57                         buffer[--len] = 0;
  58
  59                 if (len < 42 || get_sha1_hex(buffer, old_sha1) || buffer[40] != ' ')
  60                         die("protocol error: expected sha/ref, got '%s'", buffer);
  61                 name = buffer + 41;
  62
  63                 name_len = strlen(name);
  64                 if (len != name_len + 41) {
  65                         if (server_capabilities)
  66                                 free(server_capabilities);
  67                         server_capabilities = xstrdup(name + name_len + 1);
  68                 }
  69
  70                 if (!check_ref(name, name_len, flags))
  71                         continue;
  72                 if (nr_match && !path_match(name, nr_match, match))
  73                         continue;
  74                 ref = xcalloc(1, sizeof(*ref) + len - 40);
  75                 hashcpy(ref->old_sha1, old_sha1);
  76                 memcpy(ref->name, buffer + 41, len - 40);
  77                 *list = ref;
  78                 list = &ref->next;
  79         }
  80         return list;
  81 }
  82
  83 int server_supports(const char *feature)
  84 {
  85         return server_capabilities &&
  86                 strstr(server_capabilities, feature) != NULL;
  87 }
  88
  89 int get_ack(int fd, unsigned char *result_sha1)
  90 {
  91         static char line[1000];
  92         int len = packet_read_line(fd, line, sizeof(line));
  93
  94         if (!len)
  95                 die("git-fetch-pack: expected ACK/NAK, got EOF");
  96         if (line[len-1] == '\n')
  97                 line[--len] = 0;
  98         if (!strcmp(line, "NAK"))
  99                 return 0;
 100         if (!prefixcmp(line, "ACK ")) {
 101                 if (!get_sha1_hex(line+4, result_sha1)) {
 102                         if (strstr(line+45, "continue"))
 103                                 return 2;
 104                         return 1;
 105                 }
 106         }
 107         die("git-fetch_pack: expected ACK/NAK, got '%s'", line);
 108 }
 109
 110 int path_match(const char *path, int nr, char **match)
 111 {
 112         int i;
 113         int pathlen = strlen(path);
 114
 115         for (i = 0; i < nr; i++) {
 116                 char *s = match[i];
 117                 int len = strlen(s);
 118
 119                 if (!len || len > pathlen)
 120                         continue;
 121                 if (memcmp(path + pathlen - len, s, len))
 122                         continue;
 123                 if (pathlen > len && path[pathlen - len - 1] != '/')
 124                         continue;
 125                 *s = 0;
 126                 return (i + 1);
 127         }
 128         return 0;
 129 }
 130
 131 struct refspec {
 132         char *src;
 133         char *dst;
 134         char force;
 135 };
 136
 137 /*
 138  * A:B means fast forward remote B with local A.
 139  * +A:B means overwrite remote B with local A.
 140  * +A is a shorthand for +A:A.
 141  * A is a shorthand for A:A.
 142  * :B means delete remote B.
 143  */
 144 static struct refspec *parse_ref_spec(int nr_refspec, char **refspec)
 145 {
 146         int i;
 147         struct refspec *rs = xcalloc(sizeof(*rs), (nr_refspec + 1));
 148         for (i = 0; i < nr_refspec; i++) {
 149                 char *sp, *dp, *ep;
 150                 sp = refspec[i];
 151                 if (*sp == '+') {
 152                         rs[i].force = 1;
 153                         sp++;
 154                 }
 155                 ep = strchr(sp, ':');
 156                 if (ep) {
 157                         dp = ep + 1;
 158                         *ep = 0;
 159                 }
 160                 else
 161                         dp = sp;
 162                 rs[i].src = sp;
 163                 rs[i].dst = dp;
 164         }
 165         rs[nr_refspec].src = rs[nr_refspec].dst = NULL;
 166         return rs;
 167 }
 168
 169 static int count_refspec_match(const char *pattern,
 170                                struct ref *refs,
 171                                struct ref **matched_ref)
 172 {
 173         int patlen = strlen(pattern);
 174         struct ref *matched_weak = NULL;
 175         struct ref *matched = NULL;
 176         int weak_match = 0;
 177         int match = 0;
 178
 179         for (weak_match = match = 0; refs; refs = refs->next) {
 180                 char *name = refs->name;
 181                 int namelen = strlen(name);
 182                 int weak_match;
 183
 184                 if (namelen < patlen ||
 185                     memcmp(name + namelen - patlen, pattern, patlen))
 186                         continue;
 187                 if (namelen != patlen && name[namelen - patlen - 1] != '/')
 188                         continue;
 189
 190                 /* A match is "weak" if it is with refs outside
 191                  * heads or tags, and did not specify the pattern
 192                  * in full (e.g. "refs/remotes/origin/master") or at
 193                  * least from the toplevel (e.g. "remotes/origin/master");
 194                  * otherwise "git push $URL master" would result in
 195                  * ambiguity between remotes/origin/master and heads/master
 196                  * at the remote site.
 197                  */
 198                 if (namelen != patlen &&
 199                     patlen != namelen - 5 &&
 200                     prefixcmp(name, "refs/heads/") &&
 201                     prefixcmp(name, "refs/tags/")) {
 202                         /* We want to catch the case where only weak
 203                          * matches are found and there are multiple
 204                          * matches, and where more than one strong
 205                          * matches are found, as ambiguous.  One
 206                          * strong match with zero or more weak matches
 207                          * are acceptable as a unique match.
 208                          */
 209                         matched_weak = refs;
 210                         weak_match++;
 211                 }
 212                 else {
 213                         matched = refs;
 214                         match++;
 215                 }
 216         }
 217         if (!matched) {
 218                 *matched_ref = matched_weak;
 219                 return weak_match;
 220         }
 221         else {
 222                 *matched_ref = matched;
 223                 return match;
 224         }
 225 }
 226
 227 static void link_dst_tail(struct ref *ref, struct ref ***tail)
 228 {
 229         **tail = ref;
 230         *tail = &ref->next;
 231         **tail = NULL;
 232 }
 233
 234 static struct ref *try_explicit_object_name(const char *name)
 235 {
 236         unsigned char sha1[20];
 237         struct ref *ref;
 238         int len;
 239
 240         if (!*name) {
 241                 ref = xcalloc(1, sizeof(*ref) + 20);
 242                 strcpy(ref->name, "(delete)");
 243                 hashclr(ref->new_sha1);
 244                 return ref;
 245         }
 246         if (get_sha1(name, sha1))
 247                 return NULL;
 248         len = strlen(name) + 1;
 249         ref = xcalloc(1, sizeof(*ref) + len);
 250         memcpy(ref->name, name, len);
 251         hashcpy(ref->new_sha1, sha1);
 252         return ref;
 253 }
 254
 255 static int match_explicit_refs(struct ref *src, struct ref *dst,
 256                                struct ref ***dst_tail, struct refspec *rs)
 257 {
 258         int i, errs;
 259         for (i = errs = 0; rs[i].src; i++) {
 260                 struct ref *matched_src, *matched_dst;
 261
 262                 matched_src = matched_dst = NULL;
 263                 switch (count_refspec_match(rs[i].src, src, &matched_src)) {
 264                 case 1:
 265                         break;
 266                 case 0:
 267                         /* The source could be in the get_sha1() format
 268                          * not a reference name.  :refs/other is a
 269                          * way to delete 'other' ref at the remote end.
 270                          */
 271                         matched_src = try_explicit_object_name(rs[i].src);
 272                         if (matched_src)
 273                                 break;
 274                         errs = 1;
 275                         error("src refspec %s does not match any.",
 276                               rs[i].src);
 277                         break;
 278                 default:
 279                         errs = 1;
 280                         error("src refspec %s matches more than one.",
 281                               rs[i].src);
 282                         break;
 283                 }
 284                 switch (count_refspec_match(rs[i].dst, dst, &matched_dst)) {
 285                 case 1:
 286                         break;
 287                 case 0:
 288                         if (!memcmp(rs[i].dst, "refs/", 5)) {
 289                                 int len = strlen(rs[i].dst) + 1;
 290                                 matched_dst = xcalloc(1, sizeof(*dst) + len);
 291                                 memcpy(matched_dst->name, rs[i].dst, len);
 292                                 link_dst_tail(matched_dst, dst_tail);
 293                         }
 294                         else if (!strcmp(rs[i].src, rs[i].dst) &&
 295                                  matched_src) {
 296                                 /* pushing "master:master" when
 297                                  * remote does not have master yet.
 298                                  */
 299                                 int len = strlen(matched_src->name) + 1;
 300                                 matched_dst = xcalloc(1, sizeof(*dst) + len);
 301                                 memcpy(matched_dst->name, matched_src->name,
 302                                        len);
 303                                 link_dst_tail(matched_dst, dst_tail);
 304                         }
 305                         else {
 306                                 errs = 1;
 307                                 error("dst refspec %s does not match any "
 308                                       "existing ref on the remote and does "
 309                                       "not start with refs/.", rs[i].dst);
 310                         }
 311                         break;
 312                 default:
 313                         errs = 1;
 314                         error("dst refspec %s matches more than one.",
 315                               rs[i].dst);
 316                         break;
 317                 }
 318                 if (errs)
 319                         continue;
 320                 if (matched_dst->peer_ref) {
 321                         errs = 1;
 322                         error("dst ref %s receives from more than one src.",
 323                               matched_dst->name);
 324                 }
 325                 else {
 326                         matched_dst->peer_ref = matched_src;
 327                         matched_dst->force = rs[i].force;
 328                 }
 329         }
 330         return -errs;
 331 }
 332
 333 static struct ref *find_ref_by_name(struct ref *list, const char *name)
 334 {
 335         for ( ; list; list = list->next)
 336                 if (!strcmp(list->name, name))
 337                         return list;
 338         return NULL;
 339 }
 340
 341 int match_refs(struct ref *src, struct ref *dst, struct ref ***dst_tail,
 342                int nr_refspec, char **refspec, int all)
 343 {
 344         struct refspec *rs = parse_ref_spec(nr_refspec, refspec);
 345
 346         if (nr_refspec)
 347                 return match_explicit_refs(src, dst, dst_tail, rs);
 348
 349         /* pick the remainder */
 350         for ( ; src; src = src->next) {
 351                 struct ref *dst_peer;
 352                 if (src->peer_ref)
 353                         continue;
 354                 dst_peer = find_ref_by_name(dst, src->name);
 355                 if ((dst_peer && dst_peer->peer_ref) || (!dst_peer && !all))
 356                         continue;
 357                 if (!dst_peer) {
 358                         /* Create a new one and link it */
 359                         int len = strlen(src->name) + 1;
 360                         dst_peer = xcalloc(1, sizeof(*dst_peer) + len);
 361                         memcpy(dst_peer->name, src->name, len);
 362                         hashcpy(dst_peer->new_sha1, src->new_sha1);
 363                         link_dst_tail(dst_peer, dst_tail);
 364                 }
 365                 dst_peer->peer_ref = src;
 366         }
 367         return 0;
 368 }
 369
 370 enum protocol {
 371         PROTO_LOCAL = 1,
 372         PROTO_SSH,
 373         PROTO_GIT,
 374 };
 375
 376 static enum protocol get_protocol(const char *name)
 377 {
 378         if (!strcmp(name, "ssh"))
 379                 return PROTO_SSH;
 380         if (!strcmp(name, "git"))
 381                 return PROTO_GIT;
 382         if (!strcmp(name, "git+ssh"))
 383                 return PROTO_SSH;
 384         if (!strcmp(name, "ssh+git"))
 385                 return PROTO_SSH;
 386         die("I don't handle protocol '%s'", name);
 387 }
 388
 389 #define STR_(s) # s
 390 #define STR(s)  STR_(s)
 391
 392 #ifndef NO_IPV6
 393
 394 /*
 395  * Returns a connected socket() fd, or else die()s.
 396  */
 397 static int git_tcp_connect_sock(char *host, int flags)
 398 {
 399         int sockfd = -1, saved_errno = 0;
 400         char *colon, *end;
 401         const char *port = STR(DEFAULT_GIT_PORT);
 402         struct addrinfo hints, *ai0, *ai;
 403         int gai;
 404
 405         if (host[0] == '[') {
 406                 end = strchr(host + 1, ']');
 407                 if (end) {
 408                         *end = 0;
 409                         end++;
 410                         host++;
 411                 } else
 412                         end = host;
 413         } else
 414                 end = host;
 415         colon = strchr(end, ':');
 416
 417         if (colon) {
 418                 *colon = 0;
 419                 port = colon + 1;
 420                 if (!*port)
 421                         port = "<none>";
 422         }
 423
 424         memset(&hints, 0, sizeof(hints));
 425         hints.ai_socktype = SOCK_STREAM;
 426         hints.ai_protocol = IPPROTO_TCP;
 427
 428         if (flags & CONNECT_VERBOSE)
 429                 fprintf(stderr, "Looking up %s ... ", host);
 430
 431         gai = getaddrinfo(host, port, &hints, &ai);
 432         if (gai)
 433                 die("Unable to look up %s (port %s) (%s)", host, port, gai_strerror(gai));
 434
 435         if (flags & CONNECT_VERBOSE)
 436                 fprintf(stderr, "done.\nConnecting to %s (port %s) ... ", host, port);
 437
 438         for (ai0 = ai; ai; ai = ai->ai_next) {
 439                 sockfd = socket(ai->ai_family,
 440                                 ai->ai_socktype, ai->ai_protocol);
 441                 if (sockfd < 0) {
 442                         saved_errno = errno;
 443                         continue;
 444                 }
 445                 if (connect(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
 446                         saved_errno = errno;
 447                         close(sockfd);
 448                         sockfd = -1;
 449                         continue;
 450                 }
 451                 break;
 452         }
 453
 454         freeaddrinfo(ai0);
 455
 456         if (sockfd < 0)
 457                 die("unable to connect a socket (%s)", strerror(saved_errno));
 458
 459         if (flags & CONNECT_VERBOSE)
 460                 fprintf(stderr, "done.\n");
 461
 462         return sockfd;
 463 }
 464
 465 #else /* NO_IPV6 */
 466
 467 /*
 468  * Returns a connected socket() fd, or else die()s.
 469  */
 470 static int git_tcp_connect_sock(char *host, int flags)
 471 {
 472         int sockfd = -1, saved_errno = 0;
 473         char *colon, *end;
 474         char *port = STR(DEFAULT_GIT_PORT), *ep;
 475         struct hostent *he;
 476         struct sockaddr_in sa;
 477         char **ap;
 478         unsigned int nport;
 479
 480         if (host[0] == '[') {
 481                 end = strchr(host + 1, ']');
 482                 if (end) {
 483                         *end = 0;
 484                         end++;
 485                         host++;
 486                 } else
 487                         end = host;
 488         } else
 489                 end = host;
 490         colon = strchr(end, ':');
 491
 492         if (colon) {
 493                 *colon = 0;
 494                 port = colon + 1;
 495         }
 496
 497         if (flags & CONNECT_VERBOSE)
 498                 fprintf(stderr, "Looking up %s ... ", host);
 499
 500         he = gethostbyname(host);
 501         if (!he)
 502                 die("Unable to look up %s (%s)", host, hstrerror(h_errno));
 503         nport = strtoul(port, &ep, 10);
 504         if ( ep == port || *ep ) {
 505                 /* Not numeric */
 506                 struct servent *se = getservbyname(port,"tcp");
 507                 if ( !se )
 508                         die("Unknown port %s\n", port);
 509                 nport = se->s_port;
 510         }
 511
 512         if (flags & CONNECT_VERBOSE)
 513                 fprintf(stderr, "done.\nConnecting to %s (port %s) ... ", host, port);
 514
 515         for (ap = he->h_addr_list; *ap; ap++) {
 516                 sockfd = socket(he->h_addrtype, SOCK_STREAM, 0);
 517                 if (sockfd < 0) {
 518                         saved_errno = errno;
 519                         continue;
 520                 }
 521
 522                 memset(&sa, 0, sizeof sa);
 523                 sa.sin_family = he->h_addrtype;
 524                 sa.sin_port = htons(nport);
 525                 memcpy(&sa.sin_addr, *ap, he->h_length);
 526
 527                 if (connect(sockfd, (struct sockaddr *)&sa, sizeof sa) < 0) {
 528                         saved_errno = errno;
 529                         close(sockfd);
 530                         sockfd = -1;
 531                         continue;
 532                 }
 533                 break;
 534         }
 535
 536         if (sockfd < 0)
 537                 die("unable to connect a socket (%s)", strerror(saved_errno));
 538
 539         if (flags & CONNECT_VERBOSE)
 540                 fprintf(stderr, "done.\n");
 541
 542         return sockfd;
 543 }
 544
 545 #endif /* NO_IPV6 */
 546
 547
 548 static void git_tcp_connect(int fd[2], char *host, int flags)
 549 {
 550         int sockfd = git_tcp_connect_sock(host, flags);
 551
 552         fd[0] = sockfd;
 553         fd[1] = dup(sockfd);
 554 }
 555
 556
 557 static char *git_proxy_command;
 558 static const char *rhost_name;
 559 static int rhost_len;
 560
 561 static int git_proxy_command_options(const char *var, const char *value)
 562 {
 563         if (!strcmp(var, "core.gitproxy")) {
 564                 const char *for_pos;
 565                 int matchlen = -1;
 566                 int hostlen;
 567
 568                 if (git_proxy_command)
 569                         return 0;
 570                 /* [core]
 571                  * ;# matches www.kernel.org as well
 572                  * gitproxy = netcatter-1 for kernel.org
 573                  * gitproxy = netcatter-2 for sample.xz
 574                  * gitproxy = netcatter-default
 575                  */
 576                 for_pos = strstr(value, " for ");
 577                 if (!for_pos)
 578                         /* matches everybody */
 579                         matchlen = strlen(value);
 580                 else {
 581                         hostlen = strlen(for_pos + 5);
 582                         if (rhost_len < hostlen)
 583                                 matchlen = -1;
 584                         else if (!strncmp(for_pos + 5,
 585                                           rhost_name + rhost_len - hostlen,
 586                                           hostlen) &&
 587                                  ((rhost_len == hostlen) ||
 588                                   rhost_name[rhost_len - hostlen -1] == '.'))
 589                                 matchlen = for_pos - value;
 590                         else
 591                                 matchlen = -1;
 592                 }
 593                 if (0 <= matchlen) {
 594                         /* core.gitproxy = none for kernel.org */
 595                         if (matchlen == 4 &&
 596                             !memcmp(value, "none", 4))
 597                                 matchlen = 0;
 598                         git_proxy_command = xmalloc(matchlen + 1);
 599                         memcpy(git_proxy_command, value, matchlen);
 600                         git_proxy_command[matchlen] = 0;
 601                 }
 602                 return 0;
 603         }
 604
 605         return git_default_config(var, value);
 606 }
 607
 608 static int git_use_proxy(const char *host)
 609 {
 610         rhost_name = host;
 611         rhost_len = strlen(host);
 612         git_proxy_command = getenv("GIT_PROXY_COMMAND");
 613         git_config(git_proxy_command_options);
 614         rhost_name = NULL;
 615         return (git_proxy_command && *git_proxy_command);
 616 }
 617
 618 static void git_proxy_connect(int fd[2], char *host)
 619 {
 620         const char *port = STR(DEFAULT_GIT_PORT);
 621         char *colon, *end;
 622         const char *argv[4];
 623         struct child_process proxy;
 624
 625         if (host[0] == '[') {
 626                 end = strchr(host + 1, ']');
 627                 if (end) {
 628                         *end = 0;
 629                         end++;
 630                         host++;
 631                 } else
 632                         end = host;
 633         } else
 634                 end = host;
 635         colon = strchr(end, ':');
 636
 637         if (colon) {
 638                 *colon = 0;
 639                 port = colon + 1;
 640         }
 641
 642         argv[0] = git_proxy_command;
 643         argv[1] = host;
 644         argv[2] = port;
 645         argv[3] = NULL;
 646         memset(&proxy, 0, sizeof(proxy));
 647         proxy.argv = argv;
 648         proxy.in = -1;
 649         proxy.out = -1;
 650         if (start_command(&proxy))
 651                 die("cannot start proxy %s", argv[0]);
 652         fd[0] = proxy.out; /* read from proxy stdout */
 653         fd[1] = proxy.in;  /* write to proxy stdin */
 654 }
 655
 656 #define MAX_CMD_LEN 1024
 657
 658 /*
 659  * This returns 0 if the transport protocol does not need fork(2),
 660  * or a process id if it does.  Once done, finish the connection
 661  * with finish_connect() with the value returned from this function
 662  * (it is safe to call finish_connect() with 0 to support the former
 663  * case).
 664  *
 665  * Does not return a negative value on error; it just dies.
 666  */
 667 pid_t git_connect(int fd[2], char *url, const char *prog, int flags)
 668 {
 669         char *host, *path = url;
 670         char *end;
 671         int c;
 672         int pipefd[2][2];
 673         pid_t pid;
 674         enum protocol protocol = PROTO_LOCAL;
 675         int free_path = 0;
 676
 677         /* Without this we cannot rely on waitpid() to tell
 678          * what happened to our children.
 679          */
 680         signal(SIGCHLD, SIG_DFL);
 681
 682         host = strstr(url, "://");
 683         if(host) {
 684                 *host = '\0';
 685                 protocol = get_protocol(url);
 686                 host += 3;
 687                 c = '/';
 688         } else {
 689                 host = url;
 690                 c = ':';
 691         }
 692
 693         if (host[0] == '[') {
 694                 end = strchr(host + 1, ']');
 695                 if (end) {
 696                         *end = 0;
 697                         end++;
 698                         host++;
 699                 } else
 700                         end = host;
 701         } else
 702                 end = host;
 703
 704         path = strchr(end, c);
 705         if (c == ':') {
 706                 if (path) {
 707                         protocol = PROTO_SSH;
 708                         *path++ = '\0';
 709                 } else
 710                         path = host;
 711         }
 712
 713         if (!path || !*path)
 714                 die("No path specified. See 'man git-pull' for valid url syntax");
 715
 716         /*
 717          * null-terminate hostname and point path to ~ for URL's like this:
 718          *    ssh://host.xz/~user/repo
 719          */
 720         if (protocol != PROTO_LOCAL && host != url) {
 721                 char *ptr = path;
 722                 if (path[1] == '~')
 723                         path++;
 724                 else {
 725                         path = xstrdup(ptr);
 726                         free_path = 1;
 727                 }
 728
 729                 *ptr = '\0';
 730         }
 731
 732         if (protocol == PROTO_GIT) {
 733                 /* These underlying connection commands die() if they
 734                  * cannot connect.
 735                  */
 736                 char *target_host = xstrdup(host);
 737                 if (git_use_proxy(host))
 738                         git_proxy_connect(fd, host);
 739                 else
 740                         git_tcp_connect(fd, host, flags);
 741                 /*
 742                  * Separate original protocol components prog and path
 743                  * from extended components with a NUL byte.
 744                  */
 745                 packet_write(fd[1],
 746                              "%s %s%chost=%s%c",
 747                              prog, path, 0,
 748                              target_host, 0);
 749                 free(target_host);
 750                 if (free_path)
 751                         free(path);
 752                 return 0;
 753         }
 754
 755         if (pipe(pipefd[0]) < 0 || pipe(pipefd[1]) < 0)
 756                 die("unable to create pipe pair for communication");
 757         pid = fork();
 758         if (pid < 0)
 759                 die("unable to fork");
 760         if (!pid) {
 761                 char command[MAX_CMD_LEN];
 762                 char *posn = command;
 763                 int size = MAX_CMD_LEN;
 764                 int of = 0;
 765
 766                 of |= add_to_string(&posn, &size, prog, 0);
 767                 of |= add_to_string(&posn, &size, " ", 0);
 768                 of |= add_to_string(&posn, &size, path, 1);
 769
 770                 if (of)
 771                         die("command line too long");
 772
 773                 dup2(pipefd[1][0], 0);
 774                 dup2(pipefd[0][1], 1);
 775                 close(pipefd[0][0]);
 776                 close(pipefd[0][1]);
 777                 close(pipefd[1][0]);
 778                 close(pipefd[1][1]);
 779                 if (protocol == PROTO_SSH) {
 780                         const char *ssh, *ssh_basename;
 781                         ssh = getenv("GIT_SSH");
 782                         if (!ssh) ssh = "ssh";
 783                         ssh_basename = strrchr(ssh, '/');
 784                         if (!ssh_basename)
 785                                 ssh_basename = ssh;
 786                         else
 787                                 ssh_basename++;
 788                         execlp(ssh, ssh_basename, host, command, NULL);
 789                 }
 790                 else {
 791                         unsetenv(ALTERNATE_DB_ENVIRONMENT);
 792                         unsetenv(DB_ENVIRONMENT);
 793                         unsetenv(GIT_DIR_ENVIRONMENT);
 794                         unsetenv(GRAFT_ENVIRONMENT);
 795                         unsetenv(INDEX_ENVIRONMENT);
 796                         execlp("sh", "sh", "-c", command, NULL);
 797                 }
 798                 die("exec failed");
 799         }
 800         fd[0] = pipefd[0][0];
 801         fd[1] = pipefd[1][1];
 802         close(pipefd[0][1]);
 803         close(pipefd[1][0]);
 804         if (free_path)
 805                 free(path);
 806         return pid;
 807 }
 808
 809 int finish_connect(pid_t pid)
 810 {
 811         if (pid == 0)
 812                 return 0;
 813
 814         while (waitpid(pid, NULL, 0) < 0) {
 815                 if (errno != EINTR)
 816                         return -1;
 817         }
 818         return 0;
 819 }