add: version option to cli (#5)

README.md

@@ -33,6 +33,8 @@ To install `gnucash to beancount` simply use `pip`:
 pip install g2b
 ```
 
+Test with `g2b --version` if the installation was successful. 
+
 ## Usage
 
 ### Create Configuration for g2b

g2b/g2b.py

@@ -300,6 +300,7 @@ def _get_open_account_directives(self, transactions):
 
 
 @click.command()
+@click.version_option(message="%(version)s")
 @click.option(
     "--input",
     "-i",

tests/test_g2b.py

@@ -3,6 +3,7 @@
 # pylint: disable=protected-access
 import datetime
 import re
+from importlib.metadata import version
 from pathlib import Path, PosixPath
 from unittest import mock
 
@@ -52,6 +53,11 @@ def test_cli_raises_on_non_existing_config_file(self, tmp_path):
             r".*Path 'test_config.yml' does not exist.*", result.output, flags=re.DOTALL
         )
 
+    def test_cli_version(self):
+        result = self.cli_runner.invoke(main, "--version")
+        assert result.exit_code == 0, f"{result.exc_info}"
+        assert version("g2b") in result.output
+
 
 class TestGnuCash2Beancount: