+static pid_t setup_sideband(int fd[2], int xd[2])
+{
+ pid_t side_pid;
+
+ if (!use_sideband) {
+ fd[0] = xd[0];
+ fd[1] = xd[1];
+ return 0;
+ }
+ /* xd[] is talking with upload-pack; subprocess reads from
+ * xd[0], spits out band#2 to stderr, and feeds us band#1
+ * through our fd[0].
+ */
+ if (pipe(fd) < 0)
+ die("fetch-pack: unable to set up pipe");
+ side_pid = fork();
+ if (side_pid < 0)
+ die("fetch-pack: unable to fork off sideband demultiplexer");
+ if (!side_pid) {
+ /* subprocess */
+ close(fd[0]);
+ if (xd[0] != xd[1])
+ close(xd[1]);
+ if (recv_sideband("fetch-pack", xd[0], fd[1], 2))
+ exit(1);
+ exit(0);
+ }
+ close(xd[0]);
+ close(fd[1]);
+ fd[1] = xd[1];
+ return side_pid;
+}
+
+static int get_pack(int xd[2])
+{
+ int status;
+ pid_t pid, side_pid;
+ int fd[2];
+ const char *argv[20];
+ char keep_arg[256];
+ char hdr_arg[256];
+ const char **av;
+ int do_keep = keep_pack;
+
+ side_pid = setup_sideband(fd, xd);
+
+ av = argv;
+ *hdr_arg = 0;
+ if (unpack_limit) {
+ struct pack_header header;
+
+ if (read_pack_header(fd[0], &header))
+ die("protocol error: bad pack header");
+ snprintf(hdr_arg, sizeof(hdr_arg), "--pack_header=%u,%u",
+ ntohl(header.hdr_version), ntohl(header.hdr_entries));
+ if (ntohl(header.hdr_entries) < unpack_limit)
+ do_keep = 0;
+ else
+ do_keep = 1;
+ }
+
+ if (do_keep) {
+ *av++ = "index-pack";
+ *av++ = "--stdin";
+ if (!quiet)
+ *av++ = "-v";
+ if (use_thin_pack)
+ *av++ = "--fix-thin";
+ if (keep_pack > 1 || unpack_limit) {
+ int s = sprintf(keep_arg,
+ "--keep=fetch-pack %d on ", getpid());
+ if (gethostname(keep_arg + s, sizeof(keep_arg) - s))
+ strcpy(keep_arg + s, "localhost");
+ *av++ = keep_arg;
+ }
+ }
+ else {
+ *av++ = "unpack-objects";
+ if (quiet)
+ *av++ = "-q";
+ }
+ if (*hdr_arg)
+ *av++ = hdr_arg;
+ *av++ = NULL;
+
+ pid = fork();
+ if (pid < 0)
+ die("fetch-pack: unable to fork off %s", argv[0]);
+ if (!pid) {
+ dup2(fd[0], 0);
+ close(fd[0]);
+ close(fd[1]);
+ execv_git_cmd(argv);
+ die("%s exec failed", argv[0]);
+ }
+ close(fd[0]);
+ close(fd[1]);
+ while (waitpid(pid, &status, 0) < 0) {
+ if (errno != EINTR)
+ die("waiting for %s: %s", argv[0], strerror(errno));
+ }
+ if (WIFEXITED(status)) {
+ int code = WEXITSTATUS(status);
+ if (code)
+ die("%s died with error code %d", argv[0], code);
+ return 0;
+ }
+ if (WIFSIGNALED(status)) {
+ int sig = WTERMSIG(status);
+ die("%s died of signal %d", argv[0], sig);
+ }
+ die("%s died of unnatural causes %d", argv[0], status);
+}
+