$ git clone -n https://src.fedoraproject.org/forks/vondruch/rpms/rubygem-em-http-request.git /var/lib/mock/f43-build-61007916-6587597/root/chroot_tmpdir/scmroot/rubygem-em-http-request
Cloning into '/var/lib/mock/f43-build-61007916-6587597/root/chroot_tmpdir/scmroot/rubygem-em-http-request'...
$ git fetch origin a37936574e542641c23e5c94b72fa68a281b8d1c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/vondruch/rpms/rubygem-em-http-request
 * [new ref]         a37936574e542641c23e5c94b72fa68a281b8d1c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a379365 Fix compatibility with Rack 3+