feat: Add Helm 4 support alongside Helm 3

.github/copilot-instructions.md

@@ -7,7 +7,7 @@ Chartify is a Go library and CLI tool that converts Kubernetes resource YAMLs, K
 ## Working Effectively
 
 ### Bootstrap and Build
-- **Prerequisites**: Go 1.24+, Helm v3.18.6, Kustomize v5.6.0+ are required
+- **Prerequisites**: Go 1.25.4+, Helm v4.0.0, Kustomize v5.8.0+ are required
 - Build the CLI: `go build -o chartify ./cmd/chartify` -- takes 25 seconds. **NEVER CANCEL**. Set timeout to 60+ seconds.
 - Build dependencies: `go mod download` -- takes 15 seconds. **NEVER CANCEL**. Set timeout to 120+ seconds.
 - Alternative build with chart repo server: `go build -o chartreposerver ./cmd/chartreposerver`
@@ -72,7 +72,7 @@ Chartify is a Go library and CLI tool that converts Kubernetes resource YAMLs, K
 - The CLI expects exactly 2 positional arguments: RELEASE_NAME and CHART_PATH, with -o flag for output directory.
 
 ## CI/CD Integration
-- GitHub Actions run on Go 1.24+ with Helm v3.18.6 and Kustomize v5.6.0
+- GitHub Actions run on Go 1.25.4+ with Helm v4.0.0 and Kustomize v5.8.0
 - CI runs `CGO_ENABLED=0 go test ./...` after attempting to add helm stable repo
 - Linting workflow uses golangci-lint v2.1.6 but has configuration compatibility issues
 

.github/workflows/go.yml

@@ -6,8 +6,13 @@ on:
     branches: [main, master]
 jobs:
   build:
-    name: test
+    name: test (helm ${{ matrix.helm-version }})
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        helm-version:
+          - v3.19.2
+          - v4.0.0
     steps:
       - name: Check out code into the Go module directory
         uses: actions/checkout@v5
@@ -20,15 +25,16 @@ jobs:
       - name: Install Helm
         uses: azure/setup-helm@v4.3.1
         with:
-          version: v3.19.0 # default is latest (stable)
+          version: ${{ matrix.helm-version }}
 
       - name: Install Kustomize
         uses: syntaqx/setup-kustomize@v1
         with:
-          kustomize-version: 5.6.0
+          kustomize-version: 5.8.0
 
       - name: Test
         run: |
+          helm version
           helm repo add stable https://charts.helm.sh/stable
 
           CGO_ENABLED=0 go test ./...

.github/workflows/lint.yaml

@@ -24,4 +24,4 @@ jobs:
       - name: Golangci lint
         uses: golangci/golangci-lint-action@v8
         with:
-          version: v2.1.6
+          version: v2.6.2

chartify.go

@@ -11,7 +11,8 @@ import (
 
 	"github.com/Masterminds/semver/v3"
 	"github.com/otiai10/copy"
-	"helm.sh/helm/v3/pkg/registry"
+	registryv3 "helm.sh/helm/v3/pkg/registry"
+	registryv4 "helm.sh/helm/v4/pkg/registry"
 )
 
 var (
@@ -84,6 +85,10 @@ type ChartifyOpts struct {
 	// https://github.com/roboll/helmfile/issues/1547
 	SkipDeps bool
 
+	// OCIPlainHTTP uses plain HTTP for OCI registries when running helm dependency commands.
+	// Required for local/insecure OCI registries in Helm 4.
+	OCIPlainHTTP bool
+
 	// IncludeCRDs is a Helm 3 only option. When it is true, chartify passes a `--include-crds` flag
 	// to helm-template.
 	IncludeCRDs bool
@@ -378,7 +383,12 @@ func (r *Runner) Chartify(release, dirOrChart string, opts ...ChartifyOption) (s
 		} else {
 			// Flatten the chart by fetching dependent chart archives and merging their K8s manifests into the temporary local chart
 			// So that we can uniformly patch them with JSON patch, Strategic-Merge patch, or with injectors
-			_, err := r.run(nil, r.helmBin(), "dependency", "up", tempDir)
+			depArgs := []string{"dependency", "up", tempDir}
+			// Helm 4 requires --plain-http for HTTP-only OCI registries
+			if u.OCIPlainHTTP && r.IsHelm4() {
+				depArgs = append(depArgs, "--plain-http")
+			}
+			_, err := r.run(nil, r.helmBin(), depArgs...)
 			if err != nil {
 				return "", err
 			}
@@ -388,7 +398,12 @@ func (r *Runner) Chartify(release, dirOrChart string, opts ...ChartifyOption) (s
 		// and its dependencies. But ovbiously, previous `helm fetch` run doesn't download the adhoc dependencies we added
 		// after running `helm fetch`.
 		// We need to download adhoc dependencies on our own by running helmfile dependency up.
-		_, err := r.run(nil, r.helmBin(), "dependency", "up", tempDir)
+		depArgs := []string{"dependency", "up", tempDir}
+		// Helm 4 requires --plain-http for HTTP-only OCI registries
+		if u.OCIPlainHTTP && r.IsHelm4() {
+			depArgs = append(depArgs, "--plain-http")
+		}
+		_, err := r.run(nil, r.helmBin(), depArgs...)
 		if err != nil {
 			return "", err
 		}
@@ -521,7 +536,7 @@ func (r *Runner) ReadAdhocDependencies(u *ChartifyOpts) ([]Dependency, error) {
 		if isLocalChart {
 			name = filepath.Base(d.Chart)
 			repoUrl = fmt.Sprintf("file://%s", d.Chart)
-		} else if registry.IsOCI(d.Chart) {
+		} else if (r.IsHelm3() && registryv3.IsOCI(d.Chart)) || (r.IsHelm4() && registryv4.IsOCI(d.Chart)) {
 			name = filepath.Base(d.Chart)
 			// Trim trailing slash to avoid invalid repository error due to duplicate slash in oci registry url
 			// while running helm dependency up

chartify_test.go

@@ -118,7 +118,13 @@ func TestUseHelmChartsInKustomize(t *testing.T) {
 	repo := "myrepo"
 	startServer(t, repo)
 
-	r := New(UseHelm3(true), HelmBin(helm))
+	r := New(HelmBin(helm))
+
+	// Skip this test for Helm 4 as Kustomize 5.8.0 doesn't support Helm 4 yet
+	// Kustomize tries to run 'helm version -c --short' which is not supported in Helm 4
+	if r.IsHelm4() {
+		t.Skip("Skipping test: Kustomize 5.8.0 does not support Helm 4 (uses unsupported 'helm version -c' flag)")
+	}
 
 	tests := []struct {
 		name string