adding helm-diff target

Signed-off-by: hjoshi123 <mail@hjoshi.me>

Author: hjoshi123

modules/helm/helm.mk

@@ -44,6 +44,9 @@ helm_chart_sources := $(shell find $(helm_chart_source_dir) -maxdepth 1 -type f)
 helm_chart_archive := $(bin_dir)/scratch/helm/$(helm_chart_name)-$(helm_chart_version).tgz
 helm_digest_path := $(bin_dir)/scratch/helm/$(helm_chart_name)-$(helm_chart_version).digests
 helm_digest = $(shell head -1 $(helm_digest_path) 2> /dev/null)
+HELM_IGNORE_FIELDS ?= 'app.kubernetes.io/version\|helm.sh/chart\|chart:\|appVersion:\|managed-by:\|meta.helm.sh/release-namespace'
+helm_chart_old_version ?= 
+helm_chart_oci_name ?= cert-manager
 
 $(bin_dir)/scratch/helm:
 	@mkdir -p $@
@@ -187,3 +190,19 @@ verify-helm-kubeconform: $(helm_chart_archive) | $(NEEDS_KUBECONFORM)
 		-strict
 
 shared_verify_targets_dirty += verify-helm-kubeconform
+
+.PHONY: helm-diff
+helm-diff: $(helm_chart_archive) | $(NEEDS_HELM) 
+	@if [ -z "$(helm_chart_old_version)" ] then; \
+		echo "Usage: make helm-diff helm_chart_old_version=<version>"; \
+		exit 1; \
+	fi
+
+	@TMP_OLD=$$(mktemp -d);
+	@TMP_NEW=$$(mktemp -d);
+	@OUTPUT_DIR=$$(mktemp -d);
+
+	$(HELM) template $(helm_chart_oci_name) --repo "oci://$(helm_chart_image_registry)" --version "$(helm_chart_old_version)" > $${TMP_OLD}/old.yaml;
+	$(HELM) template $(helm_chart_archive) > $${TMP_NEW}/new.yaml;
+
+	diff -u <(grep -vE $(HELM_IGNORE_FIELDS) $${TMP_OLD}/old.yaml) <(grep -vE $(HELM_IGNORE_FIELDS) $${TMP_NEW}/new.yaml) | tee "$(OUTPUT_DIR)/diff.txt" || true;