$ git clone -n https://src.fedoraproject.org/rpms/glibc.git /var/lib/mock/f40-build-775810-128447/root/chroot_tmpdir/scmroot/glibc
Cloning into '/var/lib/mock/f40-build-775810-128447/root/chroot_tmpdir/scmroot/glibc'...
$ git fetch origin 0239af7b6cb8849822d7c0b6fa2ff5e87b3c8034:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/glibc
 * [new ref]         0239af7b6cb8849822d7c0b6fa2ff5e87b3c8034 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0239af7 Auto-sync with upstream branch master