$ git clone -n https://src.fedoraproject.org/rpms/rust-rmp.git /var/lib/mock/f40-build-2101574-50511/root/chroot_tmpdir/scmroot/rust-rmp
Cloning into '/var/lib/mock/f40-build-2101574-50511/root/chroot_tmpdir/scmroot/rust-rmp'...
$ git fetch origin 1f410bd5e21e69a9341a0e75b0eeacbc798ed1f5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-rmp
 * [new ref]         1f410bd5e21e69a9341a0e75b0eeacbc798ed1f5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1f410bd Update to version 0.8.12; Fixes RHBZ#2224603