feat: Environment Secrets (#274)

Resolves #255

README.md

@@ -435,6 +435,34 @@ domain: {{ .Environment.Values.domain | default "dev.example.com" }}
 `helmfile sync` installs `myapp` with the value `domain=dev.example.com`,
 whereas `helmfile --environment production sync` installs the app with the value `domain=production.example.com`.
 
+## Environment Secrets
+
+Environment Secrets are encrypted versions of `Environment Values`.
+You can list any number of `secrets.yaml` files created using `helm secrets` or `sops`, so that
+helmfile could automatically decrypt and merge the secrets into the environment values.
+
+Suppose you have environment secrets defined in `hemlfile.yaml`:
+
+```yaml
+environments:
+  production:
+    secrets:
+    - environments/produdction/secrets.yaml
+
+releases:
+- name: myapp
+  chart: mychart
+  values:
+  - values.yaml.gotmpl
+```
+
+an environment secret `foo.bar` can be referenced by the below template expression in your `values.yaml.gotmpl`:
+
+```yaml
+{{ .Values.foo.bar }
+```
+
+
 ## Separating helmfile.yaml into multiple independent files
 
 Once your `helmfile.yaml` got to contain too many releases,

state/create.go

@@ -4,10 +4,12 @@ import (
 	"fmt"
 	"github.com/imdario/mergo"
 	"github.com/roboll/helmfile/environment"
+	"github.com/roboll/helmfile/helmexec"
 	"github.com/roboll/helmfile/valuesfile"
 	"go.uber.org/zap"
 	"gopkg.in/yaml.v2"
 	"io/ioutil"
+	"os"
 	"path/filepath"
 )
 
@@ -63,6 +65,32 @@ func (state *HelmState) loadEnv(name string, readFile func(string) ([]byte, erro
 				return nil, fmt.Errorf("failed to load \"%s\": %v", envvalFile, err)
 			}
 		}
+
+		if len(envSpec.Secrets) > 0 {
+			helm := helmexec.New(state.logger, "")
+			for _, secFile := range envSpec.Secrets {
+				path := filepath.Join(state.basePath, secFile)
+				if _, err := os.Stat(path); os.IsNotExist(err) {
+					return nil, err
+				}
+
+				decFile, err := helm.DecryptSecret(path)
+				if err != nil {
+					return nil, err
+				}
+				bytes, err := readFile(decFile)
+				if err != nil {
+					return nil, fmt.Errorf("failed to load environment secrets file \"%s\": %v", secFile, err)
+				}
+				m := map[string]interface{}{}
+				if err := yaml.Unmarshal(bytes, &m); err != nil {
+					return nil, fmt.Errorf("failed to load environment secrets file \"%s\": %v", secFile, err)
+				}
+				if err := mergo.Merge(&envVals, &m, mergo.WithOverride); err != nil {
+					return nil, fmt.Errorf("failed to load \"%s\": %v", secFile, err)
+				}
+			}
+		}
 	} else if name != DefaultEnv {
 		return nil, fmt.Errorf("environment \"%s\" is not defined in \"%s\"", name, state.FilePath)
 	}

state/environment.go

@@ -1,5 +1,6 @@
 package state
 
 type EnvironmentSpec struct {
-	Values []string `yaml:"values"`
+	Values  []string `yaml:"values"`
+	Secrets []string `yaml:"secrets"`
 }