Add --indentation to vary spacing in JSON report

Some environments may want control over this to make working with
existing style-guides easier.

Co-authored-by: Jeppe Fihl-Pearson <[email protected]>

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - *Action required:* Move existing behaviour under "parse" subcommand.
   Invocations of `mypy-json-report` should now be replaced with `mypy-json-report parse`.
+- Add `parse --indentation` flag to grant control over how much indentation is used in the JSON report.
 - Use GA version of Python 3.11 in test matrix.
 
 ## v0.1.3 [2022-09-07]

mypy_json_report.py

@@ -40,6 +40,13 @@ def main() -> None:
     parse_parser = subparsers.add_parser(
         "parse", help="Transform Mypy output into JSON."
     )
+    parse_parser.add_argument(
+        "-i",
+        "--indentation",
+        type=int,
+        default=2,
+        help="Number of spaces to indent JSON output.",
+    )
 
     parse_parser.set_defaults(func=_parse_command)
 
@@ -50,7 +57,7 @@ def main() -> None:
 def _parse_command(args: argparse.Namespace) -> None:
     """Handle the `parse` command."""
     errors = parse_errors_report(sys.stdin)
-    error_json = json.dumps(errors, sort_keys=True, indent=2)
+    error_json = json.dumps(errors, sort_keys=True, indent=args.indentation)
     print(error_json)