Command methods should pass null for unmatched primitive wrapper options

[remkop]

Currently, when command methods have an option whose type is a primitive wrapper, like below:

@Command
public void cmd(@Option(names = "-x") Integer x) {}

If this command is invoked without a -x option, so the option is not matched, the value passed to the method is Integer.valueOf(0). This is correct when the option type is a primitive int, but not for an object Integer primitive wrapper.

Test to reproduce:

static class CommandMethodWithDefaults {
    @Command
    public String cmd(@Option(names = "-a", defaultValue = "2") Integer a,
                      @Option(names = "-b"                    ) Integer b,
                      @Option(names = "-c", defaultValue = "abc") String c,
                      @Option(names = "-d"                      ) String d,
                      @Option(names = "-e", defaultValue = "a=b") Map<String, String> e,
                      @Option(names = "-f"                      ) Map<String, String> f) {
        return String.format("a=%s, b=%s, c=%s, d=%s, e=%s, f=%s", a, b, c, d, e, f);
    }
}

@Test
public void testCommandMethodObjectDefaults() {
    Object s1 = CommandLine.invoke("cmd", CommandMethodWithDefaults.class);
    assertEquals("nothing matched", "a=2, b=null, c=abc, d=null, e={a=b}, f=null", s1); // fails

    Object s2 = CommandLine.invoke("cmd", CommandMethodWithDefaults.class, 
            "-a1", "-b2", "-cX", "-dY", "-eX=Y", "-fA=B");
    assertEquals("all matched", "a=1, b=2, c=X, d=Y, e={X=Y}, f={A=B}", s2);
}