$ git clone -n https://src.fedoraproject.org/rpms/rubygem-jekyll.git /var/lib/mock/f40-build-2033854-47845/root/chroot_tmpdir/scmroot/rubygem-jekyll
Cloning into '/var/lib/mock/f40-build-2033854-47845/root/chroot_tmpdir/scmroot/rubygem-jekyll'...
$ git fetch origin f198c0a25fc8c0240aeb7c7f7a0315a16947ba6c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-jekyll
 * [new ref]         f198c0a25fc8c0240aeb7c7f7a0315a16947ba6c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f198c0a Add tzdata for BuildRequires for %%check