+/*
+ * Write oid to the given struct child_process's stdin, starting it first if
+ * necessary.
+ */
+static int write_oid(const struct object_id *oid, struct packed_git *pack,
+ uint32_t pos, void *data)
+{
+ struct child_process *cmd = data;
+
+ if (cmd->in == -1) {
+ if (start_command(cmd))
+ die("Could not start pack-objects to repack promisor objects");
+ }
+
+ xwrite(cmd->in, oid_to_hex(oid), GIT_SHA1_HEXSZ);
+ xwrite(cmd->in, "\n", 1);
+ return 0;
+}
+
+static void repack_promisor_objects(const struct pack_objects_args *args,
+ struct string_list *names)
+{
+ struct child_process cmd = CHILD_PROCESS_INIT;
+ FILE *out;
+ struct strbuf line = STRBUF_INIT;
+
+ prepare_pack_objects(&cmd, args);
+ cmd.in = -1;
+
+ /*
+ * NEEDSWORK: Giving pack-objects only the OIDs without any ordering
+ * hints may result in suboptimal deltas in the resulting pack. See if
+ * the OIDs can be sent with fake paths such that pack-objects can use a
+ * {type -> existing pack order} ordering when computing deltas instead
+ * of a {type -> size} ordering, which may produce better deltas.
+ */
+ for_each_packed_object(write_oid, &cmd,
+ FOR_EACH_OBJECT_PROMISOR_ONLY);
+
+ if (cmd.in == -1)
+ /* No packed objects; cmd was never started */
+ return;
+
+ close(cmd.in);
+
+ out = xfdopen(cmd.out, "r");
+ while (strbuf_getline_lf(&line, out) != EOF) {
+ char *promisor_name;
+ int fd;
+ if (line.len != 40)
+ die("repack: Expecting 40 character sha1 lines only from pack-objects.");
+ string_list_append(names, line.buf);
+
+ /*
+ * pack-objects creates the .pack and .idx files, but not the
+ * .promisor file. Create the .promisor file, which is empty.
+ */
+ promisor_name = mkpathdup("%s-%s.promisor", packtmp,
+ line.buf);
+ fd = open(promisor_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
+ if (fd < 0)
+ die_errno("unable to create '%s'", promisor_name);
+ close(fd);
+ free(promisor_name);
+ }
+ fclose(out);
+ if (finish_command(&cmd))
+ die("Could not finish pack-objects to repack promisor objects");
+}
+