$ git clone -n https://src.fedoraproject.org/rpms/calibre.git /var/lib/mock/f41-build-735034-13218/root/chroot_tmpdir/scmroot/calibre
Cloning into '/var/lib/mock/f41-build-735034-13218/root/chroot_tmpdir/scmroot/calibre'...
$ git fetch origin 27090c4c3f20dbbcaf77cc35bf0e8ae5e43a728e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/calibre
 * [new ref]         27090c4c3f20dbbcaf77cc35bf0e8ae5e43a728e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 27090c4 Update to 7.12.0. Fixes rhbz#2284106