add catch-dotenv hook to README and improve test clarity

Author: rwbot

README.md

@@ -42,6 +42,12 @@ Require literal syntax when initializing empty or zero Python builtin types.
   - Ignore this requirement for specific builtin types with `--ignore=type1,type2,…`.
   - Forbid `dict` keyword syntax with `--no-allow-dict-kwargs`.
 
+#### `catch-dotenv`
+Prevents committing `.env` files to version control and optionally generates `.env.example` files.
+  - Use `--create-example` to generate a `.env.example` file with variable names but no values.
+  - Automatically adds `.env` to `.gitignore` if not already present.
+  - Helps prevent accidental exposure of secrets and sensitive configuration.
+
 #### `check-case-conflict`
 Check for files with names that would conflict on a case-insensitive filesystem like MacOS HFS+ or Windows FAT.
 

pre_commit_hooks/catch_dotenv.py

@@ -57,7 +57,7 @@ def _read_gitignore(gitignore_file: str) -> tuple[str, list[str]]:
             file=sys.stderr,
         )
         raise
-    return original_text if lines else '', lines
+    return original_text, lines
 
 
 def _normalize_gitignore_lines(

tests/catch_dotenv_test.py

@@ -95,7 +95,7 @@ def test_gitignore_with_existing_content_preserved(
     g = tmp_path / DEFAULT_GITIGNORE_FILE
     g.write_text(
         'node_modules/\n# comment line\n',
-    )  # no trailing newline section markers
+    )  # existing content with trailing newline
     run_hook(tmp_path, [DEFAULT_ENV_FILE])
     lines = g.read_text().splitlines()
     # original content should still be at top
@@ -372,7 +372,7 @@ def test_subdirectory_invocation(
     os.chdir(sub)
     try:
         ret = main(
-            ['../' + DEFAULT_ENV_FILE],
+            [str(Path('..') / DEFAULT_ENV_FILE)],
         )  # staged path relative to subdir
         gi = (sub / DEFAULT_GITIGNORE_FILE).read_text().splitlines()
     finally: