$ git clone -n https://src.fedoraproject.org/rpms/rust-serial_test.git /var/lib/mock/f40-build-1897557-25065/root/chroot_tmpdir/scmroot/rust-serial_test
Cloning into '/var/lib/mock/f40-build-1897557-25065/root/chroot_tmpdir/scmroot/rust-serial_test'...
$ git fetch origin 35dc32aaa30a8f7534ef41a659add31ce5f5e4a2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-serial_test
 * [new ref]         35dc32aaa30a8f7534ef41a659add31ce5f5e4a2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 35dc32a Update to version 3.1.1; Fixes RHBZ#2276319