Add editorconfig conformance checker: scripts/editorconfig-changes

[Copilot]

Builds a shell script around the editorconfig CLI that detects editorconfig violations and emits a unified diff patch — without modifying files on disk. Non-zero exit when any patch is produced makes it suitable as a CI gate or pre-commit check.

Usage

# Per-file (e.g. via fd --exec)
fd . --absolute-path --exec editorconfig-changes {}

# Batch via stdin
fd . --absolute-path | editorconfig-changes -

What it checks

Calls editorconfig <file> (single-file key=value output) per file and applies rules to a temp copy:

• trim_trailing_whitespace — sed strips trailing space/tabs per line
• end_of_line — normalises between lf / crlf / cr
• insert_final_newline — adds or removes the trailing newline byte
• charset — detects current encoding via file -b --mime-encoding, converts with iconv -f <detected> -t <target>

Binary files (detected via file --mime-encoding) and files with no editorconfig config are skipped. Quoted values (charset="utf-8") and values containing = are handled correctly.

Other changes

• tests/test_editorconfig_changes.bats — 33 BATS tests; editorconfig CLI is mocked so no real binary is required for unit testing
• .github/workflows/test-editorconfig-changes.yml — CI on macOS + Ubuntu with the real editorconfig binary installed
• brewfiles/Brewfile.all — adds editorconfig runtime dependency

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