New incremental input. With incremental: true and reuse-comment: false, each report diffs against the commit covered by the previous report instead of the base branch — so a PR with several pushes gets per-commit diffs rather than the full PR diff repeated.
The starting point is read back from the header line of the last report comment; if that commit is gone (force-push) it falls back to the base branch. Maps are now fetched at head.sha instead of head.ref, so a report is pinned to the commit it names.