Show changed files when running under --check

[charliermarsh]

Summary

We now list each changed file when running with --check.

Closes #7782.

Test Plan

❯ cargo run -p ruff_cli -- format foo.py --check
   Compiling ruff_cli v0.0.292 (/Users/crmarsh/workspace/ruff/crates/ruff_cli)
rgo +    Finished dev [unoptimized + debuginfo] target(s) in 1.41s
     Running `target/debug/ruff format foo.py --check`
warning: `ruff format` is a work-in-progress, subject to change at any time, and intended only for experimentation.
Would reformat: foo.py
1 file would be reformatted

[zanieb]

What's this look like for multiple files?

[charliermarsh]

It shows one line (like the above) per file:

File is unformatted: bar.py
File is unformatted: foo.py
2 files would be reformatted

(The filenames are bolded.)

[zanieb]

And we don't mention the files that are correctly formatted? Seems reasonable to me. Should we say "Would reformat: foo.py" instead?

[github-actions]

PR Check Results

Ecosystem

✅ ecosystem check detected no changes.

[charliermarsh]

Changed!

[zanieb]

LGTM; why the refactor?

[charliermarsh]

Which part? Overall, I needed to store the results with paths so that we could report on individual paths.

The impl<P: AsRef<Path>> From<P> change was necessary to allow passing &path to the SourceKind::from calls rather than path.as_path() -- the .as_path() shouldn't be necessary.