git hook to ensure commit doesn't break rustfmt

pre-commit

#!/usr/bin/env bash
# Put in your Rust repository's .git/hooks/pre-commit to ensure you never breaks rustfmt.                                                                                                                      

for FILE in `git diff --cached --name-only`; do
    if [[ $FILE == *.rs ]] && ! rustfmt --edition=2018 --check $FILE; then
        echo -e "\n Commit rejected due to invalid formatting of \"$FILE\" file."
        exit 1
    fi
done

rustfmt.toml

# default 2018 edition
# https://github.com/rust-lang/rustfmt/blob/master/Configurations.md#edition
edition = "2018"