Adding pyproject.toml configuration output to verbose logging (#3392)

CHANGES.md

@@ -36,6 +36,9 @@
 
 <!-- Changes to Black's terminal output and error messages -->
 
+- Verbose logging now shows the values of `pyproject.toml` configuration variables
+  (#3392)
+
 ### _Blackd_
 
 <!-- Changes to blackd -->

src/black/__init__.py

@@ -511,6 +511,9 @@ def main(  # noqa: C901
                 out("Using configuration from project root.", fg="blue")
             else:
                 out(f"Using configuration in '{config}'.", fg="blue")
+            if ctx.default_map:
+                for param, value in ctx.default_map.items():
+                    out(f"{param}: {value}")
 
     error_msg = "Oh no! 💥 💔 💥"
     if (