$ git clone -n https://src.fedoraproject.org/rpms/rubygem-gdk_pixbuf2.git /var/lib/mock/f40-build-2639127-66339/root/chroot_tmpdir/scmroot/rubygem-gdk_pixbuf2
Cloning into '/var/lib/mock/f40-build-2639127-66339/root/chroot_tmpdir/scmroot/rubygem-gdk_pixbuf2'...
$ git fetch origin 263e0666f4a99560ccfd972ba9c6f3dd038d92fa:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-gdk_pixbuf2
 * [new ref]         263e0666f4a99560ccfd972ba9c6f3dd038d92fa -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 263e066 4.2.1 entry