Added make file and root persistent flag

Makefile

@@ -0,0 +1,63 @@
+# Set the mode for code-coverage
+GO_TEST_COVERAGE_MODE ?= count
+GO_TEST_COVERAGE_FILE_NAME ?= coverage.out
+
+# Set a default `min_confidence` value for `golint`
+GO_LINT_MIN_CONFIDENCE ?= 0.2
+
+all: test
+
+.PHONY: test
+test:
+	@echo "Run unit tests"
+	@go test -v ./...
+
+.PHONY: test-with-coverage
+test-with-coverage:
+	@echo "Run unit tests with coverage"
+	@go test -cover ./...
+
+.PHONY: test-with-coverage-profile
+test-with-coverage-profile:
+	@echo "Run unit tests with coverage profile"
+	@echo "mode: ${GO_TEST_COVERAGE_MODE}" > "${GO_TEST_COVERAGE_FILE_NAME}"
+	@go test -coverpkg=`go list ./... | grep -vE 'mock' | tr '\n' ','` -covermode ${GO_TEST_COVERAGE_MODE} -coverprofile=${GO_TEST_COVERAGE_FILE_NAME} ./...
+	@echo "Generate coverage report";
+	@go tool cover -func="${GO_TEST_COVERAGE_FILE_NAME}";
+	@rm "${GO_TEST_COVERAGE_FILE_NAME}";
+
+.PHONY: fix
+fix: fix-format fix-import
+
+.PHONY: fix-import
+fix-import:
+	@echo "Fix imports"
+	@errors=$$(goimports -l -w -local $(GO_PKG) $$(go list -f "{{ .Dir }}" ./...)); if [ "$${errors}" != "" ]; then echo "$${errors}"; fi
+
+.PHONY: fix-format
+fix-format:
+	@echo "Fix formatting"
+	@gofmt -w ${GO_FMT_FLAGS} $$(go list -f "{{ .Dir }}" ./...); if [ "$${errors}" != "" ]; then echo "$${errors}"; fi
+
+.PHONY: lint
+lint: lint-format lint-import lint-style
+
+.PHONY: lint-format
+lint-format:
+	@echo "Check formatting"
+	@errors=$$(gofmt -l $$(go list -f "{{ .Dir }}" ./...)); if [ "$${errors}" != "" ]; then echo "Invalid format:\n$${errors}"; exit 1; fi
+
+.PHONY: lint-import
+lint-import:
+	@echo "Check imports"
+	@errors=$$(goimports -l $$(go list -f "{{ .Dir }}" ./...)); if [ "$${errors}" != "" ]; then echo "Invalid imports:\n$${errors}"; exit 1; fi
+
+.PHONY: lint-style
+lint-style:
+	@echo "Check code style"
+	@errors=$$(golint -min_confidence=${GO_LINT_MIN_CONFIDENCE} $$(go list ./...)); if [ "$${errors}" != "" ]; then echo "Invalid code style:\n$${errors}"; exit 1; fi
+
+.PHONY: clean
+clean:
+	@echo "Cleanup"
+	@find . -type f -name "*coverage*.out" -delete

viper.go

@@ -1,10 +1,14 @@
+// Package viper provide gozix viper bundle.
 package viper
 
 import (
+	"os"
 	"strings"
 
 	"github.com/gozix/glue"
 	"github.com/sarulabs/di"
+	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
 	"github.com/spf13/viper"
 )
 
@@ -26,8 +30,13 @@ type (
 	optionFunc func(bundle *Bundle)
 )
 
-// BundleName is default definition name.
-const BundleName = "viper"
+const (
+	// BundleName is default definition name.
+	BundleName = "viper"
+
+	// DefConfigFlag is config persistent flag name.
+	DefConfigFlag = "cli.persistent_flags.config"
+)
 
 // NewBundle create bundle instance.
 func NewBundle() *Bundle {
@@ -109,24 +118,52 @@ func (b *Bundle) Name() string {
 
 // Build implements the glue.Bundle interface.
 func (b *Bundle) Build(builder *di.Builder) error {
-	return builder.Add(di.Def{
-		Name: BundleName,
-		Build: func(ctn di.Container) (_ interface{}, err error) {
-			var registry glue.Registry
-			if err = ctn.Fill(glue.DefRegistry, &registry); err != nil {
-				return nil, err
-			}
-
-			var path string
-			if err = registry.Fill("app.path", &path); err != nil {
-				return nil, err
-			}
-
-			b.viper.AddConfigPath(path)
-
-			return b.viper, b.viper.ReadInConfig()
+	return builder.Add(
+		di.Def{
+			Name: BundleName,
+			Build: func(ctn di.Container) (_ interface{}, err error) {
+				var registry glue.Registry
+				if err = ctn.Fill(glue.DefRegistry, &registry); err != nil {
+					return nil, err
+				}
+
+				var path string
+				if err = registry.Fill("app.path", &path); err != nil {
+					return nil, err
+				}
+
+				b.viper.AddConfigPath(path)
+
+				var cmd *cobra.Command
+				if err = registry.Fill("cli.cmd", &cmd); err != nil {
+					return nil, err
+				}
+
+				var configFile string
+				if configFile, err = cmd.Flags().GetString("config"); err != nil {
+					return nil, err
+				}
+
+				if len(configFile) > 0 {
+					b.viper.SetConfigFile(configFile)
+				}
+
+				return b.viper, b.viper.ReadInConfig()
+			},
 		},
-	})
+		di.Def{
+			Name: DefConfigFlag,
+			Tags: []di.Tag{{
+				Name: glue.TagRootPersistentFlags,
+			}},
+			Build: func(_ di.Container) (i interface{}, e error) {
+				var flagSet = pflag.NewFlagSet(os.Args[0], pflag.ExitOnError)
+				flagSet.StringP("config", "c", "", "config file")
+
+				return flagSet, nil
+			},
+		},
+	)
 }
 
 // apply implements Option.