Index: head/Mk/bsd.sites.mk
===================================================================
--- head/Mk/bsd.sites.mk
+++ head/Mk/bsd.sites.mk
@@ -1580,3 +1580,44 @@
 MASTER_SITES=	${MASTER_SITES_EXP}
 
 .endif
+
+.if defined(PATCH_SITES) && ${PATCH_SITES:N*\:/*}
+
+.for _site__ in ${PATCH_SITES}
+_site_=${_site__}
+.	if ${_site_:M*\:/*}
+PATCH_SITES_EXP+=	${_site_}
+PATCH_SITES_EXP:=	${PATCH_SITES_EXP}
+.	else
+_site_urlpath_=	${_site_:C@^(.*):[^/:]+$@\1@}
+.		if ${_site_urlpath_:M*/*}
+_site_url_=		${_site_urlpath_:C@^([^/]+)/.*$@\1@}
+_site_subdir_=	${_site_urlpath_:S/^${_site_urlpath_:C@^([^/]+)/.*$@\1@}//:S!^/!!:S!/$!!}
+.		else
+_site_url_=		${_site_urlpath_}
+.undef _site_subdir_
+.		endif
+_site_group_=	${_site_:S/^${_site_:C@^(.*):[^/:]+$@\1@}//:S/^://}
+.		for _abbrev_ in ${MASTER_SITES_ABBREVS}
+.			if ${_site_url_} == ${_abbrev_:C/:.*//}
+_site_url_=	${_abbrev_:C/.*://}
+.			endif
+.		endfor
+.		for _subdir_ in ${MASTER_SITES_SUBDIRS}
+.			if ${_site_url_} == ${_subdir_:C/:.*//} && !defined(MASTER_SITE_SUBDIR)
+_site_subdir_?=	${_subdir_:C/.*://}
+.			endif
+.		endfor
+.		ifdef MASTER_SITE_${_site_url_}
+.			ifdef _site_subdir_
+PATCH_SITES_EXP+=	${MASTER_SITE_${_site_url_}:S^%SUBDIR%^${_site_subdir_}^:S/$/:${_site_group_}/:S/:$//}
+.			else
+PATCH_SITES_EXP+=	${MASTER_SITE_${_site_url_}:S/$/:${_site_group_}/:S/:$//}
+.			endif
+PATCH_SITES_EXP:=	${PATCH_SITES_EXP}
+.		endif
+.	endif
+.endfor
+PATCH_SITES=	${PATCH_SITES_EXP}
+
+.endif