Repository: pre-commit/pre-commit

Issue:
Any scalar quotes around rev are lost during autoupdate
#### Steps to reproduce

Example `.pre-commit-config.yaml`:
```
repos:
-   repo: 'https://github.com/pre-commit/pre-commit-hooks'
    rev: 'v2.4.0'
    hooks:
    -   id: 'trailing-whitespace'
    -   id: 'end-of-file-fixer'
    -   id: 'check-yaml'
    -   id: 'check-added-large-files'
```

Run 
```
$ pre-commit autoupdate
Updating https://github.com/pre-commit/pre-commit-hooks ... updating v2.4.0 -> v2.5.0.
```

`.pre-commit-config.yaml` after:
```
repos:
  - repo: 'https://github.com/pre-commit/pre-commit-hooks'
    rev: v2.5.0
    hooks:
      - id: 'trailing-whitespace'
      - id: 'end-of-file-fixer'
      - id: 'check-yaml'
      - id: 'check-added-large-files'
```
Any wrapping quotes (single or double) around the `rev` value are lost during the update

I noticed this when I turned on the `quoted-strings` [yamllint rule](https://yamllint.readthedocs.io/en/stable/rules.html#module-yamllint.rules.quoted_strings) and set it to `required` to be consistent with our internal YAML coding conventions


Discussion:

Resolving patch:
diff --git a/pre_commit/commands/autoupdate.py b/pre_commit/commands/autoupdate.py
--- a/pre_commit/commands/autoupdate.py
+++ b/pre_commit/commands/autoupdate.py
@@ -84,7 +84,9 @@ def _check_hooks_still_exist_at_rev(
         )
 
 
-REV_LINE_RE = re.compile(r'^(\s+)rev:(\s*)([^\s#]+)(.*)(\r?\n)$', re.DOTALL)
+REV_LINE_RE = re.compile(
+    r'^(\s+)rev:(\s*)([\'"]?)([^\s#]+)(.*)(\r?\n)$', re.DOTALL,
+)
 
 
 def _original_lines(
@@ -116,15 +118,15 @@ def _write_new_config(path: str, rev_infos: List[Optional[RevInfo]]) -> None:
             continue
         match = REV_LINE_RE.match(lines[idx])
         assert match is not None
-        new_rev_s = yaml_dump({'rev': rev_info.rev})
+        new_rev_s = yaml_dump({'rev': rev_info.rev}, default_style=match[3])
         new_rev = new_rev_s.split(':', 1)[1].strip()
         if rev_info.frozen is not None:
             comment = f'  # frozen: {rev_info.frozen}'
-        elif match[4].strip().startswith('# frozen:'):
+        elif match[5].strip().startswith('# frozen:'):
             comment = ''
         else:
-            comment = match[4]
-        lines[idx] = f'{match[1]}rev:{match[2]}{new_rev}{comment}{match[5]}'
+            comment = match[5]
+        lines[idx] = f'{match[1]}rev:{match[2]}{new_rev}{comment}{match[6]}'
 
     with open(path, 'w', newline='') as f:
         f.write(''.join(lines))
diff --git a/pre_commit/util.py b/pre_commit/util.py
--- a/pre_commit/util.py
+++ b/pre_commit/util.py
@@ -36,10 +36,11 @@
 Dumper = getattr(yaml, 'CSafeDumper', yaml.SafeDumper)
 
 
-def yaml_dump(o: Any) -> str:
+def yaml_dump(o: Any, **kwargs: Any) -> str:
     # when python/mypy#1484 is solved, this can be `functools.partial`
     return yaml.dump(
         o, Dumper=Dumper, default_flow_style=False, indent=4, sort_keys=False,
+        **kwargs,
     )
 
 


Test patch:
diff --git a/tests/commands/autoupdate_test.py b/tests/commands/autoupdate_test.py
--- a/tests/commands/autoupdate_test.py
+++ b/tests/commands/autoupdate_test.py
@@ -474,3 +474,23 @@ def test_updates_old_format_to_new_format(tmpdir, capsys, store):
     )
     out, _ = capsys.readouterr()
     assert out == 'Configuration has been migrated.\n'
+
+
+def test_maintains_rev_quoting_style(tmpdir, out_of_date, store):
+    fmt = (
+        'repos:\n'
+        '-   repo: {path}\n'
+        '    rev: "{rev}"\n'
+        '    hooks:\n'
+        '    -   id: foo\n'
+        '-   repo: {path}\n'
+        "    rev: '{rev}'\n"
+        '    hooks:\n'
+        '    -   id: foo\n'
+    )
+    cfg = tmpdir.join(C.CONFIG_FILE)
+    cfg.write(fmt.format(path=out_of_date.path, rev=out_of_date.original_rev))
+
+    assert autoupdate(str(cfg), store, freeze=False, tags_only=False) == 0
+    expected = fmt.format(path=out_of_date.path, rev=out_of_date.head_rev)
+    assert cfg.read() == expected