$ git clone -n https://src.fedoraproject.org/rpms/rust-buffered-reader.git /var/lib/mock/f39-build-1655419-40539/root/chroot_tmpdir/scmroot/rust-buffered-reader
Cloning into '/var/lib/mock/f39-build-1655419-40539/root/chroot_tmpdir/scmroot/rust-buffered-reader'...
$ git fetch origin b30cb923f24b50a670ece269dc062b5fe489dfac:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-buffered-reader
 * [new ref]         b30cb923f24b50a670ece269dc062b5fe489dfac -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b30cb92 Update to version 1.3.0; Fixes RHBZ#2246420