$ git clone -n https://src.fedoraproject.org/rpms/botan2.git /var/lib/mock/f40-build-2692430-68207/root/chroot_tmpdir/scmroot/botan2
Cloning into '/var/lib/mock/f40-build-2692430-68207/root/chroot_tmpdir/scmroot/botan2'...
$ git fetch origin 5d57a18f649f74e3e125aa32f52f1f9abafa5112:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/botan2
 * [new ref]         5d57a18f649f74e3e125aa32f52f1f9abafa5112 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5d57a18 Upload the src tar.