feat: Experimental Helm v3 mode

Set `HELMFILE_HELM3=1` and run `helmfile` like `HELMFILE_HELM3=1 helmfile ...`.

When `HELMFILE_HELM3` is set, `test` and `template` behaves works differently so that it works with Helm 3.

Note that `helmfile diff` doesn't work as `helm-diff` called under the hood doesn't support Helm v3 yet.

Ref #668

pkg/helmexec/exec.go

@@ -201,7 +201,14 @@ func (helm *execer) DecryptSecret(context HelmContext, name string, flags ...str
 
 func (helm *execer) TemplateRelease(name string, chart string, flags ...string) error {
 	helm.logger.Infof("Templating release=%v, chart=%v", name, chart)
-	out, err := helm.exec(append([]string{"template", chart, "--name", name}, flags...), map[string]string{})
+	var args []string
+	if helm.isHelm3() {
+		args = []string{"template", name, chart}
+	} else {
+		args = []string{"template", chart, "--name", name}
+	}
+
+	out, err := helm.exec(append(args, flags...), map[string]string{})
 	helm.write(out)
 	return err
 }
@@ -261,7 +268,13 @@ func (helm *execer) TestRelease(context HelmContext, name string, flags ...strin
 	helm.logger.Infof("Testing %v", name)
 	preArgs := context.GetTillerlessArgs(helm.helmBinary)
 	env := context.getTillerlessEnv()
-	out, err := helm.exec(append(append(preArgs, "test", name), flags...), env)
+	var args []string
+	if helm.isHelm3() {
+		args = []string{"test", "run", name}
+	} else {
+		args = []string{"test", name}
+	}
+	out, err := helm.exec(append(append(preArgs, args...), flags...), env)
 	helm.write(out)
 	return err
 }
@@ -292,3 +305,7 @@ func (helm *execer) write(out []byte) {
 		fmt.Printf("%s\n", out)
 	}
 }
+
+func (helm *execer) isHelm3() bool {
+	return os.Getenv("HELMFILE_HELM3") != ""
+}

pkg/state/state.go

@@ -930,13 +930,21 @@ func (st *HelmState) TestReleases(helm helmexec.Interface, cleanup bool, timeout
 		if cleanup {
 			flags = append(flags, "--cleanup")
 		}
-		flags = append(flags, "--timeout", strconv.Itoa(timeout))
+		duration := strconv.Itoa(timeout)
+		if st.isHelm3() {
+			duration += "s"
+		}
+		flags = append(flags, "--timeout", duration)
 		flags = st.appendConnectionFlags(flags, &release)
 
 		return helm.TestRelease(st.createHelmContext(&release, workerIndex), release.Name, flags...)
 	})
 }
 
+func (st *HelmState) isHelm3() bool {
+	return os.Getenv("HELMFILE_HELM3") != ""
+}
+
 // Clean will remove any generated secrets
 func (st *HelmState) Clean() []error {
 	errs := []error{}
@@ -1250,9 +1258,7 @@ func (st *HelmState) flagsForUpgrade(helm helmexec.Interface, release *ReleaseSp
 }
 
 func (st *HelmState) flagsForTemplate(helm helmexec.Interface, release *ReleaseSpec, workerIndex int) ([]string, error) {
-	flags := []string{
-		"--name", release.Name,
-	}
+	flags := []string{}
 
 	var err error
 	flags, err = st.appendHelmXFlags(flags, release)