zit#134: landing show has to walk the whole store to FIND the record before it can answer about it, and quarry already folded that record out of its own index. zit merge --probe names the two check-ins, so the walk disappears -- 0.005s against 0.18s on this forge's own store, and the gap widens with store size, not with the number of landings.

Probing the same tips the cache is keyed on also closes a race: the key was built from resolved tips while the probe re-resolved a branch name, so a push landing between the two cached an answer under a key it did not describe.

An unresolvable tip now skips the probe instead of keying on ':' -- every landing whose branch could not be resolved shared that one cache entry and could be served another landing's verdict. check-in: bb05986ad8 user: dmestas tags: trunk