cmdopt2/args: add acceptor builder

cmdopt2/args.cpp

@@ -95,4 +95,14 @@ keyword::present (bool &val) const
     keyword res = *this;
     res.acceptor0 = [&val] (void) { val = true; };
     return res;
+}
+
+
+//-----------------------------------------------------------------------------
+keyword
+keyword::acceptor (acceptor0_t _acceptor)
+{
+    keyword res = *this;
+    res.acceptor0 = _acceptor;
+    return res;
 }

cmdopt2/args.hpp

@@ -67,6 +67,14 @@ namespace cruft::cmdopt2 {
         {
             return reinterpret_cast<BaseT const&> (*this);
         }
+
+        BaseT
+        acceptor (acceptor1_t _acceptor) const
+        {
+            BaseT res = get ();
+            res.acceptor1 = _acceptor;
+            return res;
+        }
     };
 
 
@@ -88,6 +96,9 @@ namespace cruft::cmdopt2 {
         static keyword create (std::string const &name);
         static keyword create (std::string &&name);
 
+        using ops::acceptor;
+        keyword acceptor (acceptor0_t);
+
         keyword flag (void) const;
         keyword flag (std::string_view long_) const;
         keyword flag (char short_) const;