$ git clone -n https://src.fedoraproject.org/rpms/rust-grep-regex.git /var/lib/mock/f39-build-1891604-42794/root/chroot_tmpdir/scmroot/rust-grep-regex
Cloning into '/var/lib/mock/f39-build-1891604-42794/root/chroot_tmpdir/scmroot/rust-grep-regex'...
$ git fetch origin bdc7696a67999048e5d6cafb419719dcf7b381c7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-grep-regex
 * [new ref]         bdc7696a67999048e5d6cafb419719dcf7b381c7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bdc7696 Update to version 0.1.12; Fixes RHBZ#2251599