$ git clone -n https://src.fedoraproject.org/rpms/rust-char_str.git /var/lib/mock/f45-build-40746-775/root/chroot_tmpdir/scmroot/rust-char_str
Cloning into '/var/lib/mock/f45-build-40746-775/root/chroot_tmpdir/scmroot/rust-char_str'...
$ git fetch origin 321ae2219e26270414fa2b2b039d4f933d88b924:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-char_str
 * [new ref]         321ae2219e26270414fa2b2b039d4f933d88b924 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 321ae22 Update to version 0.0.4; Fixes RHBZ#2529485