CRITICAL data-loss bug: creating pages in Docmost (which start UNTITLED) and then
typing a title could soft-delete OTHER pages. Untitled pages all serialize to the
`_` fallback filename; the layout disambiguates them (`_.md`, `_ ~slug.md`).
Retitling one frees the bare `_` and another untitled page's file relocates into
it. git's rename detection (`-M`) can't see the move (the tiny meta-only files are
too dissimilar), so `git diff` reports it as DELETE(old) + ADD/MODIFY(new). The
push took the DELETE literally and trashed a live page.
Root cause is that the push trusted git's path-level rename heuristic for page
IDENTITY. Identity is the pageId. Fix: before emitting any delete, coalesce by
pageId — a pageId that is BOTH deleted (pre-image) AND present on the surviving
side (current meta of an ADD or a MODIFY, since a relocation into an occupied path
shows as M) is one page that MOVED, classified as a rename/move and NEVER a delete.
Reproduced + verified on a live stand: 4 untitled pages + retitle one trashed a
different page before; after the fix, retitling one (and stress-retitling all)
trashes nothing. Engine suite 598 green; 3 new computePushActions cases (ghost
D+A move -> rename; real delete still deletes; unrelated D+A stay delete+update).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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