$ git clone -n https://src.fedoraproject.org/rpms/kdegraphics-thumbnailers.git /var/lib/mock/f39-build-2166903-50992/root/chroot_tmpdir/scmroot/kdegraphics-thumbnailers
Cloning into '/var/lib/mock/f39-build-2166903-50992/root/chroot_tmpdir/scmroot/kdegraphics-thumbnailers'...
$ git fetch origin ac8e0486f9a01a93c6a5e0263f0a46373f9075c1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/kdegraphics-thumbnailers
 * [new ref]         ac8e0486f9a01a93c6a5e0263f0a46373f9075c1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ac8e048 Remove DISABLE_MOBIPOCKET=TRUE