$ git clone -n https://src.fedoraproject.org/rpms/dietlibc.git /var/lib/mock/f42-build-3528317-46309/root/chroot_tmpdir/scmroot/dietlibc
Cloning into '/var/lib/mock/f42-build-3528317-46309/root/chroot_tmpdir/scmroot/dietlibc'...
$ git fetch origin d48a6a0274454b4e78505999d9dd6c3cfedce97f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/dietlibc
 * [new ref]         d48a6a0274454b4e78505999d9dd6c3cfedce97f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d48a6a0 Fix FTBFS