more idiomatic go build time variable setting

avoiding the use of 'sed'

Makefile

@@ -4,6 +4,7 @@
 # If you can use docker without being root, you can do "make SUDO="
 SUDO=sudo
 
+WEAVE_VERSION=git-$(shell git rev-parse --short=12 HEAD)
 WEAVER_EXE=weaver/weaver
 WEAVEDNS_EXE=weavedns/weavedns
 WEAVER_IMAGE=zettio/weave
@@ -15,7 +16,7 @@ all: $(WEAVER_EXPORT) $(WEAVEDNS_EXPORT)
 
 $(WEAVER_EXE) $(WEAVEDNS_EXE):
 	go get -tags netgo ./$(shell dirname $@)
-	go build -ldflags '-extldflags "-static"' -tags netgo -o $@ ./$(shell dirname $@)
+	go build -ldflags '-extldflags "-static"' -ldflags "-X main.version $(WEAVE_VERSION)" -tags netgo -o $@ ./$(shell dirname $@)
 	@strings $@ | grep cgo_stub\\\.go >/dev/null || { \
 		rm $@; \
 		echo "\nYour go standard library was built without the 'netgo' build tag."; \

bin/release

@@ -47,11 +47,9 @@ build() {
 
     ## Inject the version numbers and build the distributables
     ## (library versions?)
-
-    sed -i "/var version = / c\var version = \"$VERSION\"" weaver/main.go
-    sed -i "/var version = / c\var version = \"$VERSION\"" weavedns/main.go
     sed -i "/SCRIPT_VERSION=/ c\SCRIPT_VERSION=\"$VERSION\"" ./weave
     make \
+        WEAVE_VERSION=$VERSION \
         WEAVER_IMAGE=$DOCKERHUB_USER/weave \
         WEAVEDNS_IMAGE=$DOCKERHUB_USER/weavedns