main: Provide additional template variables about each source path.

import2ledger/__main__.py

@@ -36,8 +36,11 @@ class FileImporter:
             raise errors.UserInputFileError("no importers available", in_file.name)
         source_vars = {
             'source_abspath': in_path.absolute().as_posix(),
+            'source_absdir': in_path.absolute().parent.as_posix(),
+            'source_dir': in_path.parent,
             'source_name': in_path.name,
             'source_path': in_path.as_posix(),
+            'source_stem': in_path.stem,
         }
         with contextlib.ExitStack() as exit_stack:
             output_path = self.config.get_output_path()