gistfile1.txt

find fp = do
    entry <- entityFromFile fp
    mold <- lookupEntity (entityHash entry)
    pure $ case mold of
        Nothing -> ImportAdded entry
        Just old | entityPath old == entityPath entry -> ImportUpToDate entry
        _ -> ImportMoved old entry
        
act (ImportAdded entry) = do
    dbPutEntity entry
    forM_ (entityPath entry) $ flip dbPutPath entry
act (ImportUpToDate entry) = pure ()
act (ImportMoved old entry) = do
    dbPutEntity old { entityPath = entityPath entry }
    forM_ (entityPath old) $ dbDel . asPathKey
    forM_ (entityPath entry) $ \path -> do
        unlinkPath path
        dbPutPath path entry