qmk_firmware/keyboards/lets_split/lets_split.h

#ifndef LETS_SPLIT_H
#define LETS_SPLIT_H

#ifdef SUBPROJECT_rev1
    #include "rev1.h"
#endif
#ifdef SUBPROJECT_rev2
    #include "rev2.h"
#endif
#ifdef SUBPROJECT_rev2fliphalf
	#include "rev2fliphalf.h"
#endif

#include "quantum.h"

#endif