[minor] add -a flag for mig-cmd that can be used to print action json

action.go

@@ -330,3 +330,13 @@ func (a Action) PrintCounters() {
 	}
 	fmt.Fprintf(os.Stderr, "%s\n", out)
 }
+
+// Return the an indented JSON string representing the action suitable for
+// display
+func (a Action) IndentedString() (string, error) {
+	buf, err := json.MarshalIndent(a, "", "    ")
+	if err != nil {
+		return "", err
+	}
+	return string(buf), nil
+}

client/mig/main.go

@@ -28,6 +28,7 @@ usage: %s <module> <global options> <module parameters>
 
 --- Global options ---
 
+-a <bool>       display action json that would be used and exit
 -c <path>	path to an alternative config file. If not set, use ~/.migrc
 -e <duration>	time after which the action expires. 60 seconds by default.
 		example: -e 300s (5 minutes)
@@ -75,6 +76,7 @@ func main() {
 		op                                             mig.Operation
 		a                                              mig.Action
 		migrc, show, render, target, expiration, afile string
+		showaction                                     bool
 		verbose                                        bool
 		modargs                                        []string
 		run                                            interface{}
@@ -87,6 +89,7 @@ func main() {
 	homedir := client.FindHomedir()
 	fs := flag.NewFlagSet("mig flag", flag.ContinueOnError)
 	fs.Usage = continueOnFlagError
+	fs.BoolVar(&showaction, "a", false, "display action json that would be used and exit")
 	fs.StringVar(&migrc, "c", homedir+"/.migrc", "alternative configuration file")
 	fs.StringVar(&show, "show", "found", "type of results to show")
 	fs.StringVar(&render, "render", "text", "results rendering mode")
@@ -121,6 +124,14 @@ func main() {
 			panic(err)
 		}
 		fmt.Fprintf(os.Stderr, "[info] launching action from file, all flags are ignored\n")
+		if showaction {
+			actionstr, err := a.IndentedString()
+			if err != nil {
+				panic(err)
+			}
+			fmt.Fprintf(os.Stdout, "%v\n", actionstr)
+			os.Exit(0)
+		}
 		goto readytolaunch
 	}
 
@@ -208,6 +219,15 @@ func main() {
 	}
 	a.Target = target
 
+	if showaction {
+		actionstr, err := a.IndentedString()
+		if err != nil {
+			panic(err)
+		}
+		fmt.Fprintf(os.Stdout, "%v\n", actionstr)
+		os.Exit(0)
+	}
+
 readytolaunch:
 	// instanciate an API client
 	conf, err = client.ReadConfiguration(migrc)