The derive built the complete effective file list for every check-in and its parent, then compared them — O(files) per check-in, which on pkgsrc is 100k entries twice over, 305k times. Fossil's add_mlink merges the two deltas' own F cards and seeks the shared baseline; do the same, and walk the lists side by side when the baselines differ instead of materializing them. Keeps recently-read manifests parsed, pinned while a step holds them.

zit#172 check-in: 669593f624 user: dmestas tags: trunk