Adds 'ginkgo outline' command

Implements feature request in onsi#753

Signed-off-by: Daniel Lipovetsky <daniel.lipovetsky@gmail.com>

ginkgo/main.go

@@ -111,6 +111,11 @@ will output an executable file named `package.test`.  This can be run directly o
 
 	ginkgo <path-to-package.test>
 
+
+To print an outline of Ginkgo specs and containers in a file:
+
+	gingko outline <filename>
+
 To print out Ginkgo's version:
 
 	ginkgo version
@@ -172,6 +177,7 @@ func init() {
 	Commands = append(Commands, BuildUnfocusCommand())
 	Commands = append(Commands, BuildVersionCommand())
 	Commands = append(Commands, BuildHelpCommand())
+	Commands = append(Commands, BuildOutlineCommand())
 }
 
 func main() {

ginkgo/outline_command.go

@@ -0,0 +1,70 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"go/parser"
+	"go/token"
+	"os"
+
+	"github.com/onsi/ginkgo/ginkgo/outline"
+)
+
+func BuildOutlineCommand() *Command {
+	const defaultFormat = "csv"
+	var format string
+	flagSet := flag.NewFlagSet("outline", flag.ExitOnError)
+	flagSet.StringVar(&format, "format", defaultFormat, "Format of outline. Accepted: 'csv', 'json'")
+	return &Command{
+		Name:         "outline",
+		FlagSet:      flagSet,
+		UsageCommand: "ginkgo outline <filename>",
+		Usage: []string{
+			"Outline of Ginkgo symbols for the file",
+		},
+		Command: func(args []string, additionalArgs []string) {
+			outlineFile(args, format)
+		},
+	}
+}
+
+func outlineFile(args []string, format string) {
+	if len(args) != 1 {
+		println("usage: ginkgo outline <filename>")
+		os.Exit(1)
+	}
+
+	filename := args[0]
+	fset := token.NewFileSet()
+
+	src, err := parser.ParseFile(fset, filename, nil, 0)
+	if err != nil {
+		println(fmt.Sprintf("error parsing source: %s", err))
+		os.Exit(1)
+	}
+
+	o, err := outline.FromASTFile(fset, src)
+	if err != nil {
+		println(fmt.Sprintf("error creating outline: %s", err))
+		os.Exit(1)
+	}
+
+	var oerr error
+	switch format {
+	case "csv":
+		_, oerr = fmt.Print(o)
+	case "json":
+		b, err := json.Marshal(o)
+		if err != nil {
+			println(fmt.Sprintf("error marshalling to json: %s", err))
+		}
+		_, oerr = fmt.Print(string(b))
+	default:
+		complainAndQuit(fmt.Sprintf("format %s not accepted", format))
+	}
+	if oerr != nil {
+		println(fmt.Sprintf("error writing outline: %s", oerr))
+		os.Exit(1)
+	}
+}