## Summary
When you run Ruff via stdin, and pass `format` or `check --fix`, we
typically write the changed or unchanged contents to stdout. It turns
out we forgot to do this when the file is _excluded_, so if you run
`ruff format /path/to/excluded/file.py`, we don't write _anything_ to
`stdout`. This led to a bug in the LSP whereby we deleted file contents
for third-party files.
The right thing to do here is write back the unchanged contents, as it
should always be safe to write the output of stdout back to a file.
## Summary
This is similar to `commands::check` vs. `commands::check_stdin`, and
gets the logic out of the parent file (`lib.rs`). It also ensures that
we avoid formatting files that should be excluded when `--force-exclude`
is provided.
