Incompatibility between state and web server

During upgrades, the new version of the tissue web server may be incompatible with the tissue state (specifically the xapian index???the document data, the slots used, etc.) built by an older version of tissue pull. At present, this will cause tissue to crash.

At the very least, tissue should produce an error message or warning so that the user can manually run a tissue pull and rebuild the state. This error message should probably appear when the tissue web server is started so that the user can take action before visitors go to a web page and find it crashed.

More ideally, it would be nice to transparently and automatically rebuild the state without the user having to know anything. But, this may be much harder to do and add more complexity. We need to decide if this additional complexity is worth it.

To implement either of these solutions, tissue must record some kind of version number in the xapian index so that it can know what version of tissue was used to build a specific index.

(made with skribilo)