coreos-go-depend: use flags to indicate what version of Go is used

sdk_container/src/third_party/coreos-overlay/eclass/coreos-go-depend.eclass

@@ -0,0 +1,30 @@
+# Copyright 2016 CoreOS, Inc.
+# Distributed under the terms of the GNU General Public License v2
+# $Header: $
+
+# @ECLASS: coreos-go-depend.eclass
+# @BLURB: Minimal Go eclass for simply depending on Go.
+
+# @ECLASS-VARIABLE: COREOS_GO_VERSION
+# @DESCRIPTION:
+# This variable specifies the version of Go to use. If ommitted the
+# default value below will be used.
+#
+# Example:
+# @CODE
+# COREOS_GO_VERSION=go1.5
+# @CODE
+export COREOS_GO_VERSION="${COREOS_GO_VERSION:-go1.6}"
+
+case "${EAPI:-0}" in
+	5|6) ;;
+	*) die "Unsupported EAPI=${EAPI} for ${ECLASS}"
+esac
+
+inherit coreos-go-utils
+
+# Set a use flag to indicate what version of Go is being used ensure
+# the package gets rebuilt when the version changes.
+IUSE="+go_version_${COREOS_GO_VERSION//./_}"
+REQUIRED_USE="go_version_${COREOS_GO_VERSION//./_}"
+DEPEND="dev-lang/go-${COREOS_GO_VERSION#go}*:="

sdk_container/src/third_party/coreos-overlay/eclass/coreos-go.eclass

@@ -6,17 +6,31 @@
 # @BLURB: utility functions for building Go binaries
 
 # @ECLASS-VARIABLE: COREOS_GO_PACKAGE
+# @REQUIRED
 # @DESCRIPTION:
-# Name of the Go package unpacked to ${S}, this is required.
+# Name of the Go package unpacked to ${S}.
+#
+# Example:
+# @CODE
+# COREOS_GO_PACKAGE="github.com/coreos/mantle"
+# @CODE
+
+# @ECLASS-VARIABLE: COREOS_GO_VERSION
+# @DESCRIPTION:
+# This variable specifies the version of Go to use. If ommitted the
+# default value from coreos-go-depend.eclass will be used.
+#
+# Example:
+# @CODE
+# COREOS_GO_VERSION=go1.5
+# @CODE
 
 case "${EAPI:-0}" in
 	5|6) ;;
 	*) die "Unsupported EAPI=${EAPI} for ${ECLASS}"
 esac
 
-inherit coreos-go-utils multiprocessing
+inherit coreos-go-depend multiprocessing
-
-DEPEND="dev-lang/go:="
 
 # @FUNCTION: go_build
 # @USAGE: <package-name> [<binary-name>]

sdk_container/src/third_party/coreos-overlay/profiles/coreos/base/make.defaults

@@ -15,6 +15,10 @@ USE_EXPAND_HIDDEN="${USE_EXPAND_HIDDEN} CROS_WORKON_TREE"
 USE_EXPAND="${USE_EXPAND} ETCD_PROTOCOLS"
 ETCD_PROTOCOLS="1 2"
 
+# Use go_version_* flags to indicate which major version was used.
+# For now this is only informational and set by coreos-go.eclass
+USE_EXPAND="${USE_EXPAND} GO_VERSION"
+
 # Extra use flags for CoreOS SDK
 USE="${USE} cros_host expat -introspection -cups -tcpd -berkdb"