swig: Modify Vars::detect_release to return char *

The original `Vars::detect_release` returns `std::unique_ptr<std::string>`
This makes it complicated for wrapping into other languages.

The modified version returns `char *` - a standard C string.

Author: jrohel

bindings/CMakeLists.txt

@@ -34,6 +34,7 @@ set(SWIG_COMPILE_OPTIONS
     -Wno-strict-aliasing
     -Wno-unused-function
     -Wno-unused-parameter
+    -Wno-unused-but-set-variable
 )
 
 if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")

bindings/libdnf5/conf.i

@@ -109,6 +109,19 @@ wrap_unique_ptr(StringUniquePtr, std::string);
 %ignore ConfigParserOptionNotFoundError;
 %include "libdnf5/conf/config_parser.hpp"
 
+%newobject libdnf5::Vars::detect_release;
+%extend libdnf5::Vars {
+  static char * detect_release(const BaseWeakPtr & base, const std::string & install_root_path) {
+    std::unique_ptr<std::string> release = libdnf5::Vars::detect_release(base, install_root_path);
+    if (release) {
+      char * release_cstr = new char[release->size() + 1];
+      strcpy(release_cstr, release->c_str());
+      return release_cstr;
+    }
+    return nullptr;
+  }
+};
+%ignore libdnf5::Vars::detect_release;
 %ignore libdnf5::ReadOnlyVariableError;
 %include "libdnf5/conf/vars.hpp"
 %template(VarsWeakPtr) libdnf5::WeakPtr<libdnf5::Vars, false>;