cargo fmt doesn't properly work on parquet crate

[alamb]

Things like

arrow-rs/parquet/src/lib.rs

Lines 137 to 138 in 54dccad

	experimental!(mod compression);
	experimental!(mod encodings);

cause entire modules to be skipped by cargo fmt.

This means that the parquet code is not properly formatted the way most rust developers would expect

cargo fmt

@etseidl added commands that do actually format the parquet crate in CI

• 25e1969 / Manually run fmt on all files under parquet #6328
• See also Is cargo fmt no longer working properly in parquet crate #6179

However it is confusing to know how to fix CI when it fails.

I agree the incantation is not desirable, and was meant to be a stop-gap until a better solution can be found.

Originally posted by @etseidl in #6886 (comment)

[etseidl]

Root cause rust-lang/rustfmt#3253