$ git clone -n https://src.fedoraproject.org/rpms/R-jsonlite.git /var/lib/mock/f39-build-1536110-36261/root/chroot_tmpdir/scmroot/R-jsonlite
Cloning into '/var/lib/mock/f39-build-1536110-36261/root/chroot_tmpdir/scmroot/R-jsonlite'...
$ git fetch origin 395c6d36d7894b9d4fd566754b9dd74f540ce5e0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-jsonlite
 * [new ref]         395c6d36d7894b9d4fd566754b9dd74f540ce5e0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 395c6d3 Update to 1.8.7