Delete name field from Command (#547)

Discussion: https://github.com/spf13/cobra/pull/422#discussion_r143918343

command.go

@@ -128,8 +128,6 @@ type Command struct {
 	// TraverseChildren parses flags on all parents before executing child command.
 	TraverseChildren bool
 
-	// name is the command name, usually the executable's name.
-	name string
 	// commands is the list of commands supported by this program.
 	commands []*Command
 	// parent is a parent command for this command.
@@ -1047,15 +1045,12 @@ func (c *Command) DebugFlags() {
 
 // Name returns the command's name: the first word in the use line.
 func (c *Command) Name() string {
-	if c.name == "" {
 	name := c.Use
 	i := strings.Index(name, " ")
 	if i >= 0 {
 		name = name[:i]
 	}
-		c.name = name
-	}
-	return c.name
+	return name
 }
 
 // HasAlias determines if a given string is an alias of the command.