$ git clone -n https://src.fedoraproject.org/rpms/gthumb.git /var/lib/mock/f41-build-808137-145687/root/chroot_tmpdir/scmroot/gthumb
Cloning into '/var/lib/mock/f41-build-808137-145687/root/chroot_tmpdir/scmroot/gthumb'...
$ git fetch origin 250df8ee53770a57ceb6a6fdfeed401c3d4ed5fc:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gthumb
 * [new ref]         250df8ee53770a57ceb6a6fdfeed401c3d4ed5fc -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 250df8e Rebuild for jpegxl (libjxl) 0.10.2