Revert "Revert "Fixes arg conflicting with group whose arg has default value""

This reverts commit 706085d9c5.

src/parse/validator.rs

@@ -284,10 +284,11 @@ impl<'help, 'app, 'parser> Validator<'help, 'app, 'parser> {
                     };
                     let conf_with_arg = || g.conflicts.iter().any(|x| !matcher.is_default_value(x));
                     let arg_conf_with_gr = || {
-                        matcher
-                            .arg_names()
-                            .filter_map(|x| self.p.app.find(x))
-                            .any(|x| x.blacklist.iter().any(|c| *c == g.id))
+                        !matcher.is_default_value(&g.id)
+                            && matcher
+                                .arg_names()
+                                .filter_map(|x| self.p.app.find(x))
+                                .any(|x| x.blacklist.iter().any(|c| *c == g.id))
                     };
                     conf_with_self() || conf_with_arg() || arg_conf_with_gr()
                 } else if let Some(ma) = matcher.get(name) {

tests/conflicts.rs

@@ -271,6 +271,29 @@ fn conflicts_with_alongside_default() {
     assert!(m.is_present("flag"));
 }
 
+#[test]
+fn group_in_conflicts_with() {
+    let result = App::new("conflict")
+        .arg(
+            Arg::new("opt")
+                .long("opt")
+                .default_value("default")
+                .group("one"),
+        )
+        .arg(Arg::new("flag").long("flag").conflicts_with("one"))
+        .try_get_matches_from(vec!["myprog", "--flag"]);
+
+    assert!(
+        result.is_ok(),
+        "conflicts_with on an arg group should ignore default_value: {:?}",
+        result.unwrap_err()
+    );
+    let m = result.unwrap();
+
+    assert_eq!(m.value_of("opt"), Some("default"));
+    assert!(m.is_present("flag"));
+}
+
 #[test]
 fn group_conflicts_with_default_arg() {
     let result = App::new("conflict")