$ git clone -n https://src.fedoraproject.org/rpms/rust-memchr.git /var/lib/mock/f40-build-2062806-49167/root/chroot_tmpdir/scmroot/rust-memchr
Cloning into '/var/lib/mock/f40-build-2062806-49167/root/chroot_tmpdir/scmroot/rust-memchr'...
$ git fetch origin 892238a57717133dc7a974fc35a60b0bdddbda51:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-memchr
 * [new ref]         892238a57717133dc7a974fc35a60b0bdddbda51 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 892238a Update to version 2.6.4; Fixes RHBZ#2241656