$ git clone -n https://src.fedoraproject.org/forks/u2fsdgvkx1/rpms/gcc.git /var/lib/mock/f45-build-290-169/root/chroot_tmpdir/scmroot/gcc
Cloning into '/var/lib/mock/f45-build-290-169/root/chroot_tmpdir/scmroot/gcc'...
$ git fetch origin fc6f68b74b459a4b88806a4ddbea1282ce11b5f0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/u2fsdgvkx1/rpms/gcc
 * [new ref]         fc6f68b74b459a4b88806a4ddbea1282ce11b5f0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fc6f68b gcc: ensure libbacktrace archive is created