Closes the branch pile-up: a catalogue branch that only adds notes now
merges into main by itself, so the work is actually in the vault rather
than waiting in a branch nobody opened.
Additive-only is measured from the diff, not assumed from the mission
type. Three conditions, all required: the type declares additive_only,
the run verified, and `git diff --name-status base...branch` contains
only A entries. A research harvest that somehow rewrote a hand-written
note is refused by the same check that lets its new notes through —
which is the case the test pins down, asserting README.md on main is
byte-identical afterwards.
Renames and deletes count as non-additive. A rename is a delete plus an
add and the delete half can destroy hand-written work.
Unknown merge_policy values fail closed to Never. A typo must not grant
auto-merge.
The diff is taken against FETCH_HEAD, freshly fetched, using `...` so an
unrelated commit landing on main meanwhile is not misread as ours. A
conflicted merge aborts and leaves the branch for a human rather than
wedging the checkout for the next run.
merge_reason is always populated and surfaced in the API: a branch that
quietly did not merge is indistinguishable from one never delivered.
399 tests, clippy clean.
Co-Authored-By: Claude Opus 5 <[email protected]>
