Index: Makefile
===================================================================
--- Makefile
+++ Makefile
@@ -153,8 +153,8 @@
 	xdev-links native-xtools native-xtools-install stageworld stagekernel \
 	stage-packages stage-packages-kernel stage-packages-world \
 	create-packages-world create-packages-kernel create-packages \
-	packages installconfig real-packages sign-packages package-pkg \
-	print-dir test-system-compiler test-system-linker
+	update-packages packages installconfig real-packages real-update-packages \
+	sign-packages package-pkg print-dir test-system-compiler test-system-linker
 
 # These targets require a TARGET and TARGET_ARCH be defined.
 XTGTS=	native-xtools native-xtools-install xdev xdev-build xdev-install \
Index: Makefile.inc1
===================================================================
--- Makefile.inc1
+++ Makefile.inc1
@@ -567,12 +567,12 @@
 .elif ${_BRANCH:M*-p*}
 EXTRA_REVISION=	_${_BRANCH:C/.*-p([0-9]+$)/\1/}
 .endif
-PKG_VERSION=	${_REVISION}${EXTRA_REVISION}
+PKG_VERSION:=	${_REVISION}${EXTRA_REVISION}
 .endif
 .endif	# !defined(PKG_VERSION)
 
 .if !defined(PKG_TIMESTAMP)
-TIMEEPOCHNOW=	%s
+TIMEEPOCHNOW=		%s
 SOURCE_DATE_EPOCH=	${TIMEEPOCHNOW:gmtime}
 .else
 SOURCE_DATE_EPOCH=	${PKG_TIMESTAMP}
@@ -1850,9 +1850,22 @@
 	@env ASSUME_ALWAYS_YES=YES pkg bootstrap
 .endif
 
+.if make(create-world-packages-jobs) || make(create-kernel-packages*) || make(real-update-packages)
+PKG_ABI!=${PKG_CMD} -o ABI_FILE=${WSTAGEDIR}/usr/bin/uname config ABI
+.endif
+
+.if !defined(PKG_VERSION_FROM)
+.if defined(PKG_ABI)
+PKG_VERSION_FROM!=/usr/bin/readlink ${REPODIR}/${PKG_ABI}/latest
+.endif
+.endif
+
 packages: .PHONY
 	${_+_}${MAKE} -C ${.CURDIR} PKG_VERSION=${PKG_VERSION} real-packages
 
+update-packages: .PHONY
+	${_+_}${MAKE} -C ${.CURDIR} PKG_VERSION=${PKG_VERSION} real-update-packages
+
 package-pkg: .PHONY
 	rm -rf /tmp/ports.${TARGET} || :
 	env ${WMAKEENV:Q} SRCDIR=${.CURDIR} PORTSDIR=${PORTSDIR} REVISION=${_REVISION} \
@@ -1862,6 +1875,29 @@
 
 real-packages:	stage-packages create-packages sign-packages .PHONY
 
+#real-update-packages: stage-packages .PHONY
+real-update-packages: .PHONY
+	${_+_}${MAKE} -C ${.CURDIR} PKG_VERSION=${PKG_VERSION} create-packages
+	@echo "==> Checking for new packages (comparing ${PKG_VERSION} to ${PKG_VERSION_FROM})"
+	@for pkg in ${REPODIR}/${PKG_ABI}/${PKG_VERSION_FROM}/${PKG_NAME_PREFIX}-*; do \
+	  pkgname=$$(pkg query -F $${pkg} '%n' | sed 's/${PKG_NAME_PREFIX}-\(.*\)/\1/') ; \
+	  newpkgname=${PKG_NAME_PREFIX}-$${pkgname}-${PKG_VERSION}.${PKG_FORMAT} ; \
+	  oldsum=$$(pkg query -F $${pkg} '%X') ; \
+	  if [ ! -f ${REPODIR}/${PKG_ABI}/${PKG_VERSION}/$${newpkgname} ]; then \
+	    continue; \
+	  fi ; \
+	  newsum=$$(pkg query -F ${REPODIR}/${PKG_ABI}/${PKG_VERSION}/$${newpkgname} '%X') ; \
+	  if [ "$${oldsum}" == "$${newsum}" ]; then \
+	   echo "==> Keeping old ${PKG_NAME_PREFIX}-$${pkgname}-${PKG_VERSION_FROM}.${PKG_FORMAT}" ; \
+	   rm ${REPODIR}/${PKG_ABI}/${PKG_VERSION}/$${newpkgname} ; \
+	   cp $${pkg} ${REPODIR}/${PKG_ABI}/${PKG_VERSION} ; \
+	  else \
+	    echo "==> New package $${newpkgname}" ; \
+	  fi ; \
+	done
+	${_+_}@cd ${.CURDIR}; \
+		${MAKE} -f Makefile.inc1 PKG_VERSION=${PKG_VERSION} sign-packages
+
 stage-packages-world: .PHONY
 	@mkdir -p ${WSTAGEDIR}
 	${_+_}@cd ${.CURDIR}; \
@@ -1912,10 +1948,6 @@
 .include "${WSTAGEDIR}/packages.mk"
 .endif
 
-.if make(create-world-packages-jobs) || make(create-kernel-packages*)
-PKG_ABI!=${PKG_CMD} -o ABI_FILE=${WSTAGEDIR}/usr/bin/uname config ABI
-.endif
-
 create-world-packages-jobs: .PHONY
 .for pkgname in ${_PKGS}
 create-world-packages-jobs: create-world-package-${pkgname}