Correct various inaccuries

command.go

@@ -25,7 +25,7 @@ func (c *Command) check() error {
 	for _, name := range c.Names {
 		for _, char := range name {
 			if !unicode.IsLetter(char) && !unicode.IsNumber(char) && char != '-' {
-				return fmt.Errorf("invalid character in flag name: %q", char)
+				return fmt.Errorf("invalid character in command name: %q in %q", char, name)
 			}
 		}
 	}

flag.go

@@ -9,7 +9,7 @@ import (
 // EmptyValue is an empty value. This is used for flags where the default value should be the empty string.
 var EmptyValue = "\000"
 
-// Flag is a string value given in the command line (or by a default value).
+// Flag is a string value given in the parameters (or by a default value).
 type Flag struct {
 	Name         string // Name of the flag.
 	Alias        rune   // Alias of the flag.