[FEATURE] recursive subcommands

include/sharg/parser.hpp

@@ -639,6 +639,19 @@ class parser
 
         operations.push_back(std::move(operation));
     }
+
+    /*!\brief Adds subcommands to the parser.
+     * \param[in] subcommands A list of subcommands.
+     */
+    void add_subcommands(std::vector<std::string> const & subcommands)
+    {
+        auto & parser_subcommands = this->subcommands;
+        parser_subcommands.insert(parser_subcommands.end(), subcommands.cbegin(), subcommands.cend());
+
+        std::ranges::sort(parser_subcommands);
+        auto const [first, last] = std::ranges::unique(parser_subcommands);
+        parser_subcommands.erase(first, last);
+    }
     //!\}
 
     /*!\brief Aggregates all parser related meta data (see sharg::parser_meta_data struct).