exclude flags from subcommand parsing

When determining the string to use when querying the radix tree for the
longest subcommand, exclude any argument beginning with a "-", since
this is a flag and not a subcommand.

This fixes a bug in which "fooasdf -o=foo" is matched to the subcommand
"foo" due to logic further down on line 704.

cli.go

@@ -680,12 +680,12 @@ func (c *CLI) processArgs() {
 				}
 
 				// Determine the argument we look to to end subcommands.
-				// We look at all arguments until one has a space. This
-				// disallows commands like: ./cli foo "bar baz". An argument
-				// with a space is always an argument.
+				// We look at all arguments until one is a flag or has a space.
+				// This disallows commands like: ./cli foo "bar baz". An
+				// argument with a space is always an argument.
 				j := 0
 				for k, v := range c.Args[i:] {
-					if strings.ContainsRune(v, ' ') {
+					if strings.ContainsRune(v, ' ') || v[0] == '-' {
 						break
 					}
 

cli_test.go

@@ -171,9 +171,6 @@ func TestCLIRun_prefix(t *testing.T) {
 	}
 }
 
-// NOTE: This failing test is intended to demonstrate incorrect behaviour
-// in which a subcommand with an arbitrary suffix is still parsed as that
-// subcommand, if a supplied argument is also suffixed by that subcommand.
 func TestCLIRun_subcommandSuffix(t *testing.T) {
 	buf := new(bytes.Buffer)
 	command := new(MockCommand)