$ git clone -n https://src.fedoraproject.org/rpms/gcc.git /var/lib/mock/f42-build-3496574-45897/root/chroot_tmpdir/scmroot/gcc
Cloning into '/var/lib/mock/f42-build-3496574-45897/root/chroot_tmpdir/scmroot/gcc'...
$ git fetch origin 976f3a74410cc70677a969b7c5838d997229c294:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gcc
 * [new ref]         976f3a74410cc70677a969b7c5838d997229c294 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 976f3a7 15.0.1-0.14