Revert "cleanup: remove all about v0.x" (#1918)

Revert "cleanup: remove all about v0.x (#1903)"

This reverts commit d7bcd5e998.

Signed-off-by: yxxhero <aiopsclub@163.com>

pkg/runtime/runtime.go

@@ -3,15 +3,24 @@ package runtime
 import (
 	"fmt"
 	"os"
+	"strconv"
 
 	"github.com/helmfile/helmfile/pkg/envvar"
 )
 
+// V1Mode is false by default for Helmfile v0.x and
+// true by default for Helmfile v1.x
 var (
+	V1Mode bool
+
 	// GoccyGoYaml is set to true in order to let Helmfile use
 	// goccy/go-yaml instead of gopkg.in/yaml.v2.
 	// It's false by default in Helmfile v0.x and true by default for Helmfile v1.x.
 	GoccyGoYaml bool
+
+	// We set this via ldflags at build-time so that we can use the
+	// value specified at the build time as the runtime default.
+	v1Mode string
 )
 
 func Info() string {
@@ -20,10 +29,22 @@ func Info() string {
 		yamlLib = "goccy/go-yaml"
 	}
 
-	return fmt.Sprintf("YAML library = %v", yamlLib)
+	return fmt.Sprintf("V1 mode = %v\nYAML library = %v", V1Mode, yamlLib)
 }
 
 func init() {
+	// You can toggle the V1 mode at runtime via an envvar:
+	// - Helmfile v1.x behaves like v0.x by running it with HELMFILE_V1MODE=false
+	// - Helmfile v0.x behaves like v1.x by with HELMFILE_V1MODE=true
+	switch os.Getenv(envvar.V1Mode) {
+	case "true":
+		V1Mode = true
+	case "false":
+		V1Mode = false
+	default:
+		V1Mode, _ = strconv.ParseBool(v1Mode)
+	}
+
 	// You can switch the YAML library at runtime via an envvar:
 	switch os.Getenv(envvar.GoccyGoYaml) {
 	case "true":
@@ -31,6 +52,6 @@ func init() {
 	case "false":
 		GoccyGoYaml = false
 	default:
-		GoccyGoYaml = true
+		GoccyGoYaml = V1Mode
 	}
 }