+/*
+ * Create "rev-list --stdin | pack-objects" pipe and feed
+ * the refs into the pipeline.
+ */
+static void rev_list_generate(int fd, struct ref *refs)
+{
+ int pipe_fd[2];
+ pid_t rev_list_generate_pid;
+
+ if (pipe(pipe_fd) < 0)
+ die("rev-list-generate setup: pipe failed");
+ rev_list_generate_pid = fork();
+ if (!rev_list_generate_pid) {
+ /* The child becomes the "rev-list | pack-objects"
+ * pipeline. It takes input from us, and its output
+ * goes to fd.
+ */
+ dup2(pipe_fd[0], 0);
+ dup2(fd, 1);
+ close(pipe_fd[0]);
+ close(pipe_fd[1]);
+ close(fd);
+ rev_list(fd, refs);
+ die("rev-list setup failed");
+ }
+ if (rev_list_generate_pid < 0)
+ die("rev-list-generate fork failed");
+
+ /* We feed the rev parameters to them. We do not write into
+ * fd nor read from the pipe.
+ */
+ close(pipe_fd[0]);
+ close(fd);
+ while (refs) {
+ char buf[42];
+
+ if (!is_null_sha1(refs->old_sha1) &&
+ has_sha1_file(refs->old_sha1)) {
+ memcpy(buf + 1, sha1_to_hex(refs->old_sha1), 40);
+ buf[0] = '^';
+ buf[41] = '\n';
+ write(pipe_fd[1], buf, 42);
+ }
+ if (!is_null_sha1(refs->new_sha1)) {
+ memcpy(buf, sha1_to_hex(refs->new_sha1), 40);
+ buf[40] = '\n';
+ write(pipe_fd[1], buf, 41);
+ }
+ refs = refs->next;
+ }
+ close(pipe_fd[1]);
+ // waitpid(rev_list_generate_pid);
+ exit(0);
+}
+
+/*
+ * Make a pack stream and spit it out into file descriptor fd
+ */