Add --list-languages flag

Signed-off-by: Lewis Marshall <[email protected]>

Author: lmars

main.go

@@ -29,6 +29,7 @@ var (
 	sortOutput   bool
 	silent       bool
 	relative     bool
+	listLangs    bool
 )
 
 // Initialize flags.
@@ -40,6 +41,7 @@ func init() {
 	flag.BoolVar(&sortOutput, "sort", true, "sort tags.")
 	flag.BoolVar(&silent, "silent", false, "do not produce any output on error.")
 	flag.BoolVar(&relative, "tag-relative", false, "file paths should be relative to the directory containing the tag file.")
+	flag.BoolVar(&listLangs, "list-languages", false, "list supported languages.")
 
 	flag.Usage = func() {
 		fmt.Fprintf(os.Stderr, "gotags version %s\n\n", Version)
@@ -133,6 +135,11 @@ func main() {
 		return
 	}
 
+	if listLangs {
+		fmt.Println("Go")
+		return
+	}
+
 	files, err := getFileNames()
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "cannot get specified files\n\n")