fix: Add missing (new) check_only argument to blacken-docs

Issue-22: #22

Author: pawamoy

Diff for: src/duty/callables/blacken_docs.py

@@ -24,6 +24,7 @@ def run(
     magic_trailing_comma: bool = True,
     python_cell_magics: set[str] | None = None,
     preview: bool = False,
+    check_only: bool = False,
 ) -> int:
     """Run `blacken-docs`.
 
@@ -44,6 +45,8 @@ def run(
             Useful for formatting cells with custom python magics.
         preview: Enable potentially disruptive style changes that may be added
             to Black's main functionality in the next major release.
+        check_only: Don't modify files but indicate when changes are necessary
+            with a message and non-zero return code.
 
     Returns:
         Success/failure.
@@ -80,5 +83,6 @@ def run(
             black_mode,
             skip_errors=skip_errors,
             rst_literal_blocks=rst_literal_blocks,
+            check_only=check_only,
         )
     return retv

Diff for: src/duty/tools/_blacken_docs.py

@@ -29,6 +29,7 @@ def __init__(
         magic_trailing_comma: bool = True,
         python_cell_magics: set[str] | None = None,
         preview: bool = False,
+        check_only: bool = False,
     ) -> None:
         """Run `blacken-docs`.
 
@@ -49,6 +50,8 @@ def __init__(
                 Useful for formatting cells with custom python magics.
             preview: Enable potentially disruptive style changes that may be added
                 to Black's main functionality in the next major release.
+            check_only: Don't modify files but indicate when changes are necessary
+                with a message and non-zero return code.
 
         Returns:
             Success/failure.
@@ -77,6 +80,7 @@ def __call__(self) -> int:
         preview = self.py_args["preview"]
         skip_errors = self.py_args["skip_errors"]
         rst_literal_blocks = self.py_args["rst_literal_blocks"]
+        check_only = self.py_args["check_only"]
 
         # Build filepaths.
         exts = ("md", "py") if exts is None else tuple(ext.lstrip(".") for ext in exts)
@@ -111,5 +115,6 @@ def __call__(self) -> int:
                 black_mode,
                 skip_errors=skip_errors,
                 rst_literal_blocks=rst_literal_blocks,
+                check_only=check_only,
             )
         return retv