build: Download CRD deps only when necessary

Create individual make targets for the CRD dependencies so that make can
identify that the CRD dependencies have already been downloaded and
skip. When the SOURCE_VER changes, old CRDs are deleted and new ones are
downloaded, keeping a record of the source CRD versions in
build/.src-crd-<version> by file name.
Also, introduce `cleanup-crd-deps` make target to delete the previously
downloaded CRDs.

Signed-off-by: Sunny <darkowlzz@protonmail.com>

Makefile

@@ -34,6 +34,15 @@ BUILD_PLATFORMS ?= linux/amd64
 # Architecture to use envtest with
 ENVTEST_ARCH ?= amd64
 
+# Paths to download the CRD dependencies at.
+GITREPO_CRD ?= config/crd/bases/gitrepositories.yaml
+BUCKET_CRD ?= config/crd/bases/buckets.yaml
+OCIREPO_CRD ?= config/crd/bases/ocirepositories.yaml
+
+# Keep a record of the version of the downloaded source CRDs. It is used to
+# detect and download new CRDs when the SOURCE_VER changes.
+SOURCE_CRD_VER=$(BUILD_DIR)/.src-crd-$(SOURCE_VER)
+
 all: manager
 
 # Download the envtest binaries to testbin
@@ -60,11 +69,28 @@ manager: generate fmt vet
 run: generate fmt vet manifests
 	go run ./main.go --metrics-addr=:8089
 
+# Delete previously downloaded CRDs and record the new version of the source
+# CRDs.
+$(SOURCE_CRD_VER):
+	rm -f $(BUILD_DIR)/.src-crd*
+	$(MAKE) cleanup-crd-deps
+	touch $(SOURCE_CRD_VER)
+
+$(GITREPO_CRD):
+	curl -s https://raw.githubusercontent.com/fluxcd/source-controller/${SOURCE_VER}/config/crd/bases/source.toolkit.fluxcd.io_gitrepositories.yaml -o $(GITREPO_CRD)
+
+$(BUCKET_CRD):
+	curl -s https://raw.githubusercontent.com/fluxcd/source-controller/${SOURCE_VER}/config/crd/bases/source.toolkit.fluxcd.io_buckets.yaml -o $(BUCKET_CRD)
+
+$(OCIREPO_CRD):
+	curl -s https://raw.githubusercontent.com/fluxcd/source-controller/${SOURCE_VER}/config/crd/bases/source.toolkit.fluxcd.io_ocirepositories.yaml -o $(OCIREPO_CRD)
+
 # Download the CRDs the controller depends on
-download-crd-deps:
-	curl -s https://raw.githubusercontent.com/fluxcd/source-controller/${SOURCE_VER}/config/crd/bases/source.toolkit.fluxcd.io_gitrepositories.yaml > config/crd/bases/gitrepositories.yaml
-	curl -s https://raw.githubusercontent.com/fluxcd/source-controller/${SOURCE_VER}/config/crd/bases/source.toolkit.fluxcd.io_buckets.yaml > config/crd/bases/buckets.yaml
-	curl -s https://raw.githubusercontent.com/fluxcd/source-controller/${SOURCE_VER}/config/crd/bases/source.toolkit.fluxcd.io_ocirepositories.yaml > config/crd/bases/ocirepositories.yaml
+download-crd-deps: $(SOURCE_CRD_VER) $(GITREPO_CRD) $(BUCKET_CRD) $(OCIREPO_CRD)
+
+# Delete the downloaded CRD dependencies.
+cleanup-crd-deps:
+	rm -f $(GITREPO_CRD) $(BUCKET_CRD) $(OCIREPO_CRD)
 
 # Install CRDs into a cluster
 install: manifests