$ git clone -n https://src.fedoraproject.org/rpms/magic.git /var/lib/mock/f41-build-side-1-3132749-39664/root/chroot_tmpdir/scmroot/magic
Cloning into '/var/lib/mock/f41-build-side-1-3132749-39664/root/chroot_tmpdir/scmroot/magic'...
$ git fetch origin e3c129cc3fc40574ec14666a737005d60312a5d1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/magic
 * [new ref]         e3c129cc3fc40574ec14666a737005d60312a5d1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e3c129c 8.3.499