fix(helm): stop processing if lint can't find a chart

This exits with an error code if the path resolution fails to find a
chart.

cmd/helm/lint.go

@@ -1,7 +1,10 @@
 package main
 
 import (
+	"errors"
 	"fmt"
+	"os"
+	"path/filepath"
 
 	"github.com/kubernetes/helm/pkg/lint"
 	"github.com/spf13/cobra"
@@ -20,20 +23,29 @@ var lintCommand = &cobra.Command{
 	Use:   "lint [flags] PATH",
 	Short: "Examines a chart for possible issues",
 	Long:  longLintHelp,
-	Run:   lintCmd,
+	RunE:  lintCmd,
 }
 
 func init() {
 	RootCommand.AddCommand(lintCommand)
 }
 
-func lintCmd(cmd *cobra.Command, args []string) {
+var errLintNoChart = errors.New("no chart found for linting (missing Chart.yaml).")
+
+func lintCmd(cmd *cobra.Command, args []string) error {
 	path := "."
 	if len(args) > 0 {
 		path = args[0]
 	}
+
+	// Guard: Error out of this is not a chart.
+	if _, err := os.Stat(filepath.Join(path, "Chart.yaml")); err != nil {
+		return errLintNoChart
+	}
+
 	issues := lint.All(path)
 	for _, i := range issues {
 		fmt.Printf("%s\n", i)
 	}
+	return nil
 }