Add: Add a get_commands function to return all VersionCommand classes

Better abstract the available VersionCommand classes by providing a
function to get access to them.

pontos/version/commands.py

@@ -15,7 +15,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from typing import Tuple, Type
+from typing import Iterable, Tuple, Type
 
 from pontos.version.errors import ProjectError
 
@@ -47,3 +47,7 @@ def gather_project() -> VersionCommand:
             return command
 
     raise ProjectError("No project settings file found")
+
+
+def get_commands() -> Iterable[Type[VersionCommand]]:
+    return _COMMANDS

tests/version/test_commands.py

@@ -19,7 +19,7 @@
 
 from pontos.testing import temp_directory, temp_python_module
 from pontos.version.cmake import CMakeVersionCommand
-from pontos.version.commands import gather_project
+from pontos.version.commands import gather_project, get_commands
 from pontos.version.errors import ProjectError
 from pontos.version.go import GoVersionCommand
 from pontos.version.javascript import JavaScriptVersionCommand
@@ -71,3 +71,8 @@ def test_cmake_project_version(self):
             version_file.write_text("project(VERSION 1.2.3)", encoding="utf8")
 
             self.assertIsInstance(gather_project(), CMakeVersionCommand)
+
+
+class GetCommandsTestCase(unittest.TestCase):
+    def test_available_commands(self):
+        self.assertEqual(len(get_commands()), 4)