$ git clone -n https://src.fedoraproject.org/rpms/rubygem-webrick.git /var/lib/mock/f45-build-35407-695/root/chroot_tmpdir/scmroot/rubygem-webrick
Cloning into '/var/lib/mock/f45-build-35407-695/root/chroot_tmpdir/scmroot/rubygem-webrick'...
$ git fetch origin 0dc851321f5e7a517b11d8ccc8b79812515d2458:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-webrick
 * [new ref]         0dc851321f5e7a517b11d8ccc8b79812515d2458 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0dc8513 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild