fix(App, Args): fixed subcommand reqs negation

Closes #188

src/app.rs

@@ -2391,7 +2391,7 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
             self.print_help();
             self.exit(1);
         }
-        if (!self.subcmds_neg_reqs) && self.validate_required(&matches) {
+        if ((!self.subcmds_neg_reqs) || matches.subcommand_name().is_none()) && self.validate_required(&matches) {
             self.report_error(format!("The following required arguments were not \
                 supplied:{}",
                 self.get_required_from(self.required.iter()

src/lib.rs

@@ -27,7 +27,7 @@ mod fmt;
 
 #[cfg(test)]
 mod tests {
-    use super::{App, Arg, SubCommand};
+    use super::{App, Arg, SubCommand, AppSettings};
     use std::collections::HashSet;
     use std::vec::Vec;
 
@@ -1255,4 +1255,16 @@ mod tests {
         App::new("short_flag")
             .arg(Arg::from_usage("-f 'some flag'"));
     }
+
+    #[test]
+    fn sub_command_negate_requred() {
+        App::new("sub_command_negate")
+            .setting(AppSettings::SubcommandsNegateReqs)
+            .arg(Arg::with_name("test")
+                   .required(true)
+                   .index(1))
+            .subcommand(SubCommand::with_name("sub1"))
+            .subcommand(SubCommand::with_name("sub1"))
+            .get_matches_from(vec!["", "sub1"]);
+    }
 }