Generate version from git tag

This drop the need to maintain a separate version file.

See also: kubernetes#1198

Makefile

@@ -1,15 +1,13 @@
 FLAGS =
 TESTENVVAR =
 REGISTRY ?= gcr.io/k8s-staging-kube-state-metrics
-TAG_PREFIX = v
-VERSION = $(shell cat VERSION)
-TAG = $(TAG_PREFIX)$(VERSION)
-LATEST_RELEASE_BRANCH := release-$(shell grep -ohE "[0-9]+.[0-9]+" VERSION)
+TAG ?= $(shell git describe --abbrev=0 --tags 2>/dev/null)
+LATEST_RELEASE_BRANCH := release-$(shell echo $(TAG) | grep -ohE "[0-9]+.[0-9]+")
 DOCKER_CLI ?= docker
 PKGS = $(shell go list ./... | grep -v /vendor/ | grep -v /tests/e2e)
 ARCH ?= $(shell go env GOARCH)
 BuildDate = $(shell date -u +'%Y-%m-%dT%H:%M:%SZ')
-Commit = $(shell git rev-parse --short HEAD)
+Commit = $(shell git rev-parse --short HEAD 2>/dev/null)
 ALL_ARCH = amd64 arm arm64 ppc64le s390x
 PKG = k8s.io/kube-state-metrics/pkg
 GO_VERSION = 1.14.7

RELEASE.md

@@ -14,7 +14,7 @@ Maintaining the release branches for older minor releases happens on a best effo
 
 ## Prepare your release
 
-* Bump the version in the `VERSION` file in the root of the repository.
+* Create a git tag locally
 * Run `make examples`, which will re-generate all example manifests to use the new version.
 * Make a PR to update:
   * kube-state-metrics image tag for both `quay.io` and `gcr.io/k8s-staging-kube-state-metrics`.