Multi-level logging (#185)

Closes #93

Summary of changes:

- Adds the [uber-go-/zap](https://github.com/uber-go/zap) library for leveled logging (69040996e0bcbd2f211d0d8d576147027e928e3b)
- A new CLI arg `--log-level` which can take the values `debug` `info` `warn` `error` `fatal` `panic`. The default is `info`, and the existing `--quiet` flag is treated as `--log-level warn`
- All `helm.exec` calls are preceded by a one-line summary. The current information on the full helm command line arguments `exec: helm exec ... ` is only output at `debug` level. This means sensitive command line arguments which may include passwords and `--set` arguments should be hidden by default.

main.go

@@ -2,18 +2,20 @@ package main
 
 import (
 	"fmt"
-	"io"
 	"log"
 	"os"
 	"os/signal"
 	"strings"
 	"syscall"
 
+	"path/filepath"
+	"sort"
+
 	"github.com/roboll/helmfile/helmexec"
 	"github.com/roboll/helmfile/state"
 	"github.com/urfave/cli"
-	"path/filepath"
-	"sort"
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 )
 
 const (
@@ -24,6 +26,28 @@ const (
 
 var Version string
 
+func configure_logging(c *cli.Context) error {
+	// Valid levels:
+	// https://github.com/uber-go/zap/blob/7e7e266a8dbce911a49554b945538c5b950196b8/zapcore/level.go#L126
+	logLevel := c.GlobalString("log-level")
+	if c.GlobalBool("quiet") {
+		logLevel = "warn"
+	}
+	var level zapcore.Level
+	err := level.Set(logLevel)
+	if err != nil {
+		return err
+	}
+	logger := helmexec.NewLogger(os.Stdout, logLevel)
+	if c.App.Metadata == nil {
+		// Auto-initialised in 1.19.0
+		// https://github.com/urfave/cli/blob/master/CHANGELOG.md#1190---2016-11-19
+		c.App.Metadata = make(map[string]interface{})
+	}
+	c.App.Metadata["logger"] = logger
+	return nil
+}
+
 func main() {
 
 	app := cli.NewApp()
@@ -42,12 +66,16 @@ func main() {
 		},
 		cli.BoolFlag{
 			Name:  "quiet, q",
-			Usage: "silence output",
+			Usage: "Silence output. Equivalent to log-level warn",
 		},
 		cli.StringFlag{
 			Name:  "kube-context",
 			Usage: "Set kubectl context. Uses current context by default",
 		},
+		cli.StringFlag{
+			Name:  "log-level",
+			Usage: "Set log level, default info",
+		},
 		cli.StringFlag{
 			Name:  "namespace, n",
 			Usage: "Set namespace. Uses the namespace set in the context by default",
@@ -61,6 +89,7 @@ func main() {
 		},
 	}
 
+	app.Before = configure_logging
 	app.Commands = []cli.Command{
 		{
 			Name:  "repos",
@@ -422,7 +451,6 @@ func directoryExistsAt(path string) bool {
 }
 
 func loadDesiredStateFromFile(c *cli.Context, file string) (*state.HelmState, helmexec.Interface, error) {
-	quiet := c.GlobalBool("quiet")
 	kubeContext := c.GlobalString("kube-context")
 	namespace := c.GlobalString("namespace")
 	labels := c.GlobalStringSlice("selector")
@@ -455,10 +483,6 @@ func loadDesiredStateFromFile(c *cli.Context, file string) (*state.HelmState, he
 			os.Exit(1)
 		}
 	}
-	var writer io.Writer
-	if !quiet {
-		writer = os.Stdout
-	}
 
 	sigs := make(chan os.Signal, 1)
 	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
@@ -469,7 +493,8 @@ func loadDesiredStateFromFile(c *cli.Context, file string) (*state.HelmState, he
 		clean(st, errs)
 	}()
 
-	return st, helmexec.New(writer, kubeContext), nil
+	logger := c.App.Metadata["logger"].(*zap.SugaredLogger)
+	return st, helmexec.New(logger, kubeContext), nil
 }
 
 func clean(state *state.HelmState, errs []error) error {