use textwrap.indent instead of _indent

pre_commit/commands/migrate_config.py

@@ -1,4 +1,5 @@
 import re
+import textwrap
 
 import yaml
 
@@ -6,11 +7,6 @@ from pre_commit.clientlib import load_config
 from pre_commit.util import yaml_load
 
 
-def _indent(s: str) -> str:
-    lines = s.splitlines(True)
-    return ''.join(' ' * 4 + line if line.strip() else line for line in lines)
-
-
 def _is_header_line(line: str) -> bool:
     return line.startswith(('#', '---')) or not line.strip()
 
@@ -34,7 +30,7 @@ def _migrate_map(contents: str) -> str:
             yaml_load(trial_contents)
             contents = trial_contents
         except yaml.YAMLError:
-            contents = f'{header}repos:\n{_indent(rest)}'
+            contents = f'{header}repos:\n{textwrap.indent(rest, " " * 4)}'
 
     return contents
 

tests/commands/migrate_config_test.py

@@ -2,24 +2,9 @@ import pytest
 
 import pre_commit.constants as C
 from pre_commit.clientlib import InvalidConfigError
-from pre_commit.commands.migrate_config import _indent
 from pre_commit.commands.migrate_config import migrate_config
 
 
-@pytest.mark.parametrize(
-    ('s', 'expected'),
-    (
-        ('', ''),
-        ('a', '    a'),
-        ('foo\nbar', '    foo\n    bar'),
-        ('foo\n\nbar\n', '    foo\n\n    bar\n'),
-        ('\n\n\n', '\n\n\n'),
-    ),
-)
-def test_indent(s, expected):
-    assert _indent(s) == expected
-
-
 def test_migrate_config_normal_format(tmpdir, capsys):
     cfg = tmpdir.join(C.CONFIG_FILE)
     cfg.write(