$ git clone -n https://src.fedoraproject.org/rpms/clean-rpm-gpg-pubkey.git /var/lib/mock/f42-build-side-1-3537718-46560/root/chroot_tmpdir/scmroot/clean-rpm-gpg-pubkey
Cloning into '/var/lib/mock/f42-build-side-1-3537718-46560/root/chroot_tmpdir/scmroot/clean-rpm-gpg-pubkey'...
$ git fetch origin 25e4da85cee2c5c6626801c2fa5ec78495ed548b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/clean-rpm-gpg-pubkey
 * [new ref]         25e4da85cee2c5c6626801c2fa5ec78495ed548b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 25e4da8 Update to commit fc87e2c.