ensure controller-gen exists and is minimum right version

Makefile

@@ -2,6 +2,8 @@
 
 KUBEBUILDER_VERSION ?= 2.3.1
 KUBEBUILDER ?= /usr/local/kubebuilder/bin/kubebuilder
+CONTROLLER_GEN_VERSION ?= v0.3.0
+CONTROLLER_GEN=$(GOBIN)/controller-gen
 
 CERTMANAGER_URL ?= https://github.com/jetstack/cert-manager/releases/download/v0.14.1/cert-manager.yaml
 
@@ -179,20 +181,11 @@ push:
 
 # find or download controller-gen
 # download controller-gen if necessary
-controller-gen:
-ifeq (, $(shell which controller-gen))
-	@{ \
-	set -e ;\
-	CONTROLLER_GEN_TMP_DIR=$$(mktemp -d) ;\
-	cd $$CONTROLLER_GEN_TMP_DIR ;\
-	go mod init tmp ;\
-	go get sigs.k8s.io/controller-tools/cmd/controller-gen@v0.2.5 ;\
-	rm -rf $$CONTROLLER_GEN_TMP_DIR ;\
-	}
-CONTROLLER_GEN=$(GOBIN)/controller-gen
-else
-CONTROLLER_GEN=$(shell which controller-gen)
-endif
+# version must be at least the given version
+.PHONY: $(CONTROLLER_GEN)
+controller-gen: $(CONTROLLER_GEN)
+$(CONTROLLER_GEN):
+	scripts/controller-gen.sh $@ $(CONTROLLER_GEN_VERSION)
 
 examples:
 	./generate-examples.sh

scripts/controller-gen.sh

@@ -0,0 +1,82 @@
+#!/bin/sh
+
+set -e
+
+# ensure controller-gen is at least the right version
+
+
+download() {
+	local version=$1
+	local P=$(pwd)
+	local TMP_DIR=$(mktemp -d)
+	cd $TMP_DIR
+	go mod init tmp
+	go get -u sigs.k8s.io/controller-tools/cmd/controller-gen@${version}
+	cd ${P}
+
+	# clean up the temporary working directory
+	rm -rf $TMP_DIR
+}
+
+# see if the first semver argument is >= the second semver argument
+later() {
+	local compare=$1
+	local base=$2
+	# strip off the optional "v" at the beginning
+	compare=${compare#v}
+	base=${base#v}
+
+	local compareMajor=${compare%%.*}
+	local baseMajor=${base%%.*}
+
+	local compareMinorPatch=${compare#*.}
+	local baseMinorPatch=${base#*.}
+
+	local compareMinor=${compareMinorPatch%%.*}
+	local baseMinor=${baseMinorPatch%%.*}
+
+	local comparePatch=${compare##*.}
+	local basePatch=${base##*.}
+	# check major version
+
+	# start with major - if greater, it is later; if less, it is earlier
+	[ $compareMajor -lt $baseMajor ] && return 1
+	[ $compareMajor -gt $baseMajor ] && return 0
+
+	# major matches, so check minor	
+	[ $compareMinor -lt $baseMinor ] && return 1
+	[ $compareMinor -gt $baseMinor ] && return 0
+
+	# minor matches, so check patch
+	[ $comparePatch -lt $basePatch ] && return 1
+	[ $comparePatch -gt $basePatch ] && return 0
+
+	# patch matches, so it is the same
+	return 0
+}
+
+
+BINARY=$1
+VERSION=$2
+
+# if no version given, just download the latest and go
+if [ -z "$VERSION" ]; then
+	download master
+	exit 0
+fi
+
+# check if we have one and what its version is
+if [ ! -e "${BINARY}" ]; then
+	download ${VERSION}
+	exit 0
+fi
+
+# if we got here, we have one, and we were not asked to take latest, so check its version
+existing=$(${BINARY} --version | awk '{print $2}')
+# get the three parts of the semver and the three parts of the requested version, and compare
+
+later "${existing}" "${VERSION}" || download ${VERSION}
+
+exit 0
+
+