fix(onset): merges never declare one thing twice, and match git wherever git is clean

Radin committed …

⧉1c2a1da0ca97

Author

Radin · radin@coline.appOct 31, 2026 at 21:10

Committer

Radin · radin@coline.appOct 31, 2026 at 21:27

Parents

b2c8186aaa9d

fix(onset): merges never declare one thing twice, and match git wherever git is clean

The smart merge kept both sides wherever both added at one spot, so two
different `def helper` landed as two definitions and `timeout:` landed twice
in one YAML map, both silently. It also missed its own headline case: two new
JS functions still conflicted on their shared closing braces.

- core/decls.rs reads what a file declares (functions, classes, members by
  scope; YAML, JSON, TOML, .env and INI keys). A merge that declares
  something more times than either side did is a conflict, even where the
  lines didn't touch and git calls it clean; sync marks the change's spot.
- Both-added blocks merge only when each is whole declarations or test
  cases with nothing in common; statements keep git's conflict. Imports
  binding one name twice conflict. Entries added to a sorted list go in
  sorted.
- A property test checks 4,000 random merges per file type: where git's
  line merge is clean, Onset's is byte-identical. A fuzz test checks the
  scanner and merges never panic (it found a slice past a short line).
- examples/merge_corpus replays a repository's merges: on 4,000 of git's
  own, 6,416/6,416 clean files identical; of 576 conflicts its maintainer
  resolved, 37 settled as he did, 530 left, 9 differing only in order or
  blank lines. On this repository it catches a duplicated pnpm-lock entry
  git merged silently and a person fixed by hand.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>