Add containerdVersion flag

Add version flag that only prints the static version for the binary.

This commit does not include build details for containers since
Makefile does not build them.

Closes #8

Signed-off-by: Christopher M. Luciano <cmluciano@us.ibm.com>

Makefile

@@ -17,6 +17,9 @@ EPOCH_TEST_COMMIT ?= f9e02affccd51702191e5312665a16045ffef8ab
 PROJECT := github.com/kubernetes-incubator/cri-containerd
 BINDIR ?= ${DESTDIR}/usr/local/bin
 BUILD_DIR ?= _output
+# VERSION is the version of the binary.
+VERSION:=$(shell git describe --tags --dirty)
+BUILD_TAGS:= -ldflags '-X $(PROJECT)/pkg/version.criContainerdVersion=$(VERSION)'
 
 all: binaries
 
@@ -32,6 +35,7 @@ help:
 	@echo " * 'verify'        - Execute the source code verification tools"
 	@echo " * 'install.tools' - Installs tools used by verify"
 	@echo " * 'uninstall'     - Remove installed binaries from system locations"
+	@echo " * 'version'       - Print current cri-containerd release version"
 
 .PHONY: check-gopath
 
@@ -42,6 +46,9 @@ endif
 
 verify: lint gofmt boiler
 
+version:
+	@echo $(VERSION)
+
 lint: check-gopath
 	@echo "checking lint"
 	@./hack/lint.sh
@@ -56,7 +63,8 @@ boiler:
 
 cri-containerd: check-gopath
 	$(GO) build -o $(BUILD_DIR)/$@ \
-		$(PROJECT)/cmd/cri-containerd
+        $(BUILD_TAGS) \
+	$(PROJECT)/cmd/cri-containerd
 
 test: 
 	go test -timeout=1m -v -race ./pkg/... $(BUILD_TAGS)
@@ -102,4 +110,5 @@ install.tools: .install.gitvalidation .install.gometalinter
 	help \
 	install \
 	lint \
-	uninstall
+	uninstall \
+	version