Quote Each Path in Both Refusals, So a Space or Comma Cannot Read as a Separator

Both messages joined raw paths with commas, so a single path holding a
comma read as two and one holding a space read ambiguously. That is worst
exactly when the message matters, since it fires on a path the caller did
not expect to be there.

One `quoted` helper serves both, rather than a repr at each site, since the
two messages drifting apart is the smaller version of the problem this PR
is about.

Two cases added, one per message.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: ptr727

scripts/prose_lint.py

@@ -199,6 +199,15 @@ def repo_prefix(root: Path) -> str:
     return r.stdout.strip() if r.returncode == 0 else ''
 
 
+def quoted(paths) -> str:
+    """Paths as a sorted, quoted, comma-joined list for an error message.
+
+    Quoted because a path holding a space or a comma is indistinguishable from two paths once
+    joined, which makes the message unreadable exactly when it names something unexpected.
+    """
+    return ', '.join(repr(str(p)) for p in sorted(paths))
+
+
 def repo_root(path: Path) -> str:
     """The repository top level containing `path`, or '' when git cannot say."""
     start = path if path.is_dir() else path.parent
@@ -1114,16 +1123,16 @@ def main(argv: list[str] | None = None) -> int:
     # `discover` reads a non-file, non-directory argument as `.`, so a typo scanned the caller's directory while the rule set anchored on the missing path's parent.
     absent = [p for p in scan_paths if not Path(p).exists()]
     if absent:
-        print(f"error: requested path(s) do not exist: {', '.join(sorted(absent))}. Refusing "
-              'rather than falling back to the current directory, which would scan one tree and '
-              'choose the rule set from another.', file=sys.stderr)
+        # Quoted, since a path holding a space or a comma is unreadable in a bare comma-joined list.
+        print(f"error: requested path(s) do not exist: {quoted(absent)}. Refusing rather than "
+              'falling back to the current directory, which would scan one tree and choose the '
+              'rule set from another.', file=sys.stderr)
         return 2
     git_roots = {found for found in (repo_root(Path(p)) for p in scan_paths) if found}
     if len(git_roots) > 1:
-        print('error: the requested paths span more than one repository (' +
-              ', '.join(sorted(git_roots)) + '). Each declares its own workflow model, so no '
-              'single rule set is correct for all of them. Run the gate once per repository.',
-              file=sys.stderr)
+        print(f'error: the requested paths span more than one repository ({quoted(git_roots)}). '
+              'Each declares its own workflow model, so no single rule set is correct for all of '
+              'them. Run the gate once per repository.', file=sys.stderr)
         return 2
     # A file anchors on its own parent rather than on `.`, which is where the caller stands.
     if git_roots:

scripts/test_prose_lint.py

@@ -1868,6 +1868,21 @@ def test_a_path_that_does_not_exist_is_refused_rather_than_absorbed(self) -> Non
                 [str(self.tmp / 'no-such-dir'), '--check', 'home-path']))
         self.assertIn('do not exist', self.err.getvalue())
 
+    def test_a_path_holding_a_space_or_comma_is_quoted_in_the_refusal(self) -> None:
+        """Joined bare, one path with a comma in it reads as two paths and the message misleads."""
+        awkward = self.tmp / 'a dir, with comma'
+        with mock.patch.object(prose_lint, 'repo_root', return_value=''):
+            self.assertEqual(2, prose_lint.main([str(awkward), '--check', 'home-path']))
+        self.assertIn(repr(str(awkward)), self.err.getvalue())
+
+    def test_repository_roots_are_quoted_in_the_span_refusal(self) -> None:
+        spaced = self.tmp / 'root with space'
+        spaced.mkdir()
+        with mock.patch.object(prose_lint, 'repo_root', side_effect=lambda p: str(Path(p))):
+            self.assertEqual(2, prose_lint.main(
+                [str(self.release), str(spaced), '--check', 'home-path']))
+        self.assertIn(repr(str(spaced)), self.err.getvalue())
+
     def test_an_existing_path_is_not_refused_by_that_check(self) -> None:
         """The guard must not reject the ordinary case it sits in front of."""
         good = self.tmp / 'good.md'