Pass global flags down to subcommands

Fix #51

Signed-off-by: Andrew Thornton <art27@cantab.net>

main.go

@@ -71,6 +71,29 @@ func main() {
 		},
 	}
 
+	for _, command := range app.Commands {
+		originalFlagNames := make([]string, 0, len(command.Flags))
+		for _, flag := range command.Flags {
+			originalFlagNames = append(originalFlagNames, flag.Names()...)
+		}
+
+		for _, flag := range app.Flags {
+			found := false
+		flagNameLoop:
+			for _, name := range flag.Names() {
+				for _, originalName := range originalFlagNames {
+					if name == originalName {
+						found = true
+						break flagNameLoop
+					}
+				}
+			}
+			if !found {
+				command.Flags = append(command.Flags, flag)
+			}
+		}
+	}
+
 	if err := app.Run(os.Args); err != nil {
 		fmt.Printf("Failed to run app with %s: %v\n", os.Args[1:], err)
 	}