Fix Argument bool bit fields

The intent of ": 1" is to use individual bits to store the bool state of
these class values. Because true != 0, this worked. But it was likely to
bite someone sometime. (My bad: 0fe17e2.)

This commit also adds m_accepts_optional_like_value to the bit field and
sets the default false value in the constructor.

Because we cannot set a default value during declaration (until C++20).
make sure future coders know to set the preferred default in the
constructor.

Closes #213

Signed-off-by: Sean Robinson <[email protected]>

include/argparse/argparse.hpp

@@ -376,7 +376,8 @@ class Argument {
   explicit Argument(std::string_view prefix_chars,
                     std::array<std::string_view, N> &&a,
                     std::index_sequence<I...> /*unused*/)
-      : m_is_optional((is_optional(a[I], prefix_chars) || ...)),
+      : m_accepts_optional_like_value(false),
+        m_is_optional((is_optional(a[I], prefix_chars) || ...)),
         m_is_required(false), m_is_repeatable(false), m_is_used(false),
         m_prefix_chars(prefix_chars) {
     ((void)m_names.emplace_back(a[I]), ...);
@@ -1037,11 +1038,12 @@ class Argument {
       [](const std::string &value) { return value; }};
   std::vector<std::any> m_values;
   NArgsRange m_num_args_range{1, 1};
-  bool m_accepts_optional_like_value = false;
-  bool m_is_optional : true;
-  bool m_is_required : true;
-  bool m_is_repeatable : true;
-  bool m_is_used : true; // True if the optional argument is used by user
+  // Bit field of bool values. Set default value in ctor.
+  bool m_accepts_optional_like_value : 1;
+  bool m_is_optional : 1;
+  bool m_is_required : 1;
+  bool m_is_repeatable : 1;
+  bool m_is_used : 1;
   std::string_view m_prefix_chars; // ArgumentParser has the prefix_chars
 };