`--write` wrote CHANGELOG.md and then removed fragments one by one, so a
failure after the write left surviving fragments that a rerun spliced in
a second time.
The write is now staged. The assembled file goes into
changelog.d/.assembling/, the fragments are renamed in beside it, and
renaming the assembled file over CHANGELOG.md is the single commit
point. A run that fails rolls itself back when it can; otherwise the next
`npm run changelog` reads the staging directory and either restores the
fragments (assembled file still staged) or deletes the leftovers (batch
landed). `--check` reports a staged batch instead of reporting past it.
A failure-injection test makes every filesystem call in a `--write` fail
in turn, both as a one-off error and as a crash with no in-process
rollback. It asserts the retry produces exactly the uninterrupted
CHANGELOG.md, with each entry once and an empty directory. The test
fails against the previous write-then-delete and against delete-first.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
`CONTRIBUTING.md` asks every runtime change to add an entry at the top of
`CHANGELOG.md`, so two pull requests in flight write into the same few lines and
git has nothing to merge on. Against `main` at `81eb443`, `git merge-tree` over
the 85 open pull requests GitHub reports as conflicting that aren't mine puts
`CHANGELOG.md` in the conflict set of 41 — more than any other path — and for 6
it is the only one. `docs/CURRENT-STATE.md`, the other file rule 3 names,
conflicts for 23, and merges cleanly for 23 of the 41: edits land in the section
for the area you touched, so they only collide when the areas do.
A pull request now adds `changelog.d/<pull request>-<slug>.md` instead. Distinct
filenames never conflict, and the pull request number makes them distinct for
free. `npm run changelog` splices the directory into `CHANGELOG.md` and empties
it; `npm run changelog:check` reports the batch and changes nothing.
Fragment text is copied through unchanged apart from trailing whitespace.
`src/annotations/drawTool.test.mjs` reads `CHANGELOG.md` as prose and slices a
fixed window after a heading, so an assembler that reflowed an entry could move
text across that window. Fragments are deliberately outside
`scripts/format-scope.json` for the same reason.
The assembler refuses a batch before writing anything when a filename is not
`<pull request>-<slug>.md` or two fragments claim one pull request number, and
a unit test runs that check over the real `changelog.d/`, so a fragment the
release could not assemble fails `npm test` in the pull request that adds it
rather than at release time.
Refs #781.
