$ git clone -n https://src.fedoraproject.org/rpms/libretro-bsnes-mercury.git /var/lib/mock/f40-build-2008254-45356/root/chroot_tmpdir/scmroot/libretro-bsnes-mercury
Cloning into '/var/lib/mock/f40-build-2008254-45356/root/chroot_tmpdir/scmroot/libretro-bsnes-mercury'...
$ git fetch origin 4683feaf4f8dc4daf47be2c767a9f1715c8ab1df:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libretro-bsnes-mercury
 * [new ref]         4683feaf4f8dc4daf47be2c767a9f1715c8ab1df -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4683fea build: DEBUG=1