fncache: document the fact fncache is outdate at hook run time Using 'addfinalize' to generate 'fncache' means that no pending version of the file will be generated for the hooks. We would have to use the 'addfilegenerator' method to get such result. However the 'fncachevfs' (who decide that a write is necessary) have no access to the transaction to register such file generation at add time. Having the transaction accessible to the 'vfs' is too much trouble for no benefit. This outdated 'fncache' file at hook time is not expected to be an issue. The previous move from 'onclose' to 'addfinalize' had no impact on this timing. I'm documenting it now because I looked at it.