$ git clone -n https://src.fedoraproject.org/rpms/calibre.git /var/lib/mock/f40-build-735276-106332/root/chroot_tmpdir/scmroot/calibre
Cloning into '/var/lib/mock/f40-build-735276-106332/root/chroot_tmpdir/scmroot/calibre'...
$ git fetch origin fef6bd5f5c9acd2f0c2b0af28f4a7effea1b7db5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/calibre
 * [new ref]         fef6bd5f5c9acd2f0c2b0af28f4a7effea1b7db5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fef6bd5 Update to 6.29.0. Fixes rhbz#2245238