$ git clone -n https://src.fedoraproject.org/rpms/calibre.git /var/lib/mock/f39-build-2317188-58088/root/chroot_tmpdir/scmroot/calibre
Cloning into '/var/lib/mock/f39-build-2317188-58088/root/chroot_tmpdir/scmroot/calibre'...
$ git fetch origin 9ebfd0b78193b7ed48603003c66d8ffecb4740f8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/calibre
 * [new ref]         9ebfd0b78193b7ed48603003c66d8ffecb4740f8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9ebfd0b Version 7.3.0