Since the implemenation of rc.subr, a lot of ports have adapted the
system and the quality of the startup/shutdown/status scripts have
increased. But a lot of duplicate code has grown into the ports
Makefiles to make sure that the startup scripts got installed
properly.

Look at the additional www/apache2 port overhead:

USE_RC_SUBR=            yes
RC_SCRIPTS_SUB= PREFIX=${PREFIX} RC_SUBR=${RC_SUBR}
post-patch:
    @${SED} ${RC_SCRIPTS_SUB:S/$/!g/:S/^/ -e s!%%/:S/=/%%!/} \
	${FILESDIR}/apache.sh > ${WRKDIR}/apache2.sh
    .if !defined(WITH_APR_FROM_PORTS)
    @${SED} ${RC_SCRIPTS_SUB:S/$/!g/:S/^/ -e s!%%/:S/=/%%!/} \
	${FILESDIR}/apache2libs.sh > ${WRKDIR}/apache2libs.sh
    .endif

post-install:
.if !defined(WITH_APR_FROM_PORTS)
    @${ECHO_CMD} "Installing ${PREFIX}/etc/rc.d/000.apache2libs.sh startup script."
    @${INSTALL_SCRIPT} -m 751 ${WRKDIR}/apache2libs.sh ${PREFIX}/etc/rc.d/000.apache2libs.sh
.endif
    @${ECHO_CMD} "Installing ${PREFIX}/etc/rc.d/apache2.sh startup script."
    @${INSTALL_SCRIPT} -m 751 ${WRKDIR}/apache2.sh ${PREFIX}/etc/rc.d/apache2.sh


Imagine every port which uses rc.subr to have these identical
additional lines to it, that's not really making life easier to
maintain.

Imagine the following configuration:

	USE_RC_SUBR=	yes
	RC_FILES=	apache2.sh
	.if !defined(WITH_APR_FROM_PORTS)
	RC_FILES+=	apache2libs.sh
	.endif

And bsd.port.mk would automaticly do the patching, installation and
pkg-plist additions!

The patch attached is harmless for ports which don't use this new
system (since the trigger isn't USE_RC_SUBR but RC_FILES).

The patch does....

- It patches the files defined in RC_FILES with the variables defined
  in RC_SUBST (LOCALBASE, PREFIX, RC_SUBR, X11BASE by default).
- It installs the files defined in RC_FILES to PREFIX/etc/rc.d
- It adds the files defined in RC_FILES to the PKGPLIST.