Almost all of find_fix's time went to git child processes: one merge-base per hit (2105 x 132 ms for a broad --grep), a single-threaded git log --all -S, and one branch --contains per printed candidate, run one after another. One rev-list HEAD set now decides in_head, -S runs as strided slices of rev-list --all through a thread pool and is sorted back into git log --all order, and the candidate lines are built in parallel. Output stays byte-identical on four real calls (3x to 142x faster). Tests pin the -S order and that the filters are alternatives.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
