--diff unexpectedly performs the ssort on the file

[AndydeCleyre]

Hello, and thanks!

Testing with 0.15.0, --diff, in addition to showing the diff as expected, performs the changes on the file.

This is unexpected because:

• the flag description is (emphasis added):

  Prints a diff of all changes ssort would make to a file.

• similar commands, including ruff format --diff, ruff check --fix --diff, yapf --diff, autopep8 --diff, and black --diff, do not change the file when --diff is passed.

[bwhmather]

Ah! Current behaviour what I thought black and isort did. Have been running them for years with --check --diff, but you are right that the --check is redundant.

I'll update to match.