$ git clone -n https://src.fedoraproject.org/rpms/thunderbird.git /var/lib/mock/f41-build-side-1-2949561-35473/root/chroot_tmpdir/scmroot/thunderbird
Cloning into '/var/lib/mock/f41-build-side-1-2949561-35473/root/chroot_tmpdir/scmroot/thunderbird'...
$ git fetch origin c134918953fcc3d7e0dd2ff57af28f46d0fa1889:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/thunderbird
 * [new ref]         c134918953fcc3d7e0dd2ff57af28f46d0fa1889 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c134918 Update to 128.3.1