$ git clone -n https://src.fedoraproject.org/rpms/rust-grep.git /var/lib/mock/f38-build-side-43-rust-devel-1399216-31127/root/chroot_tmpdir/scmroot/rust-grep
Cloning into '/var/lib/mock/f38-build-side-43-rust-devel-1399216-31127/root/chroot_tmpdir/scmroot/rust-grep'...
$ git fetch origin b1a9c96b2981640de4a7453fbefb5763f41cd5f4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-grep
 * [new ref]         b1a9c96b2981640de4a7453fbefb5763f41cd5f4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b1a9c96 Update to version 0.2.12; Fixes RHBZ#2207747