Let's acknowledge everyone's contributions by replacing "Google LLC"
in the copyright header by "The Jujutsu Authors". If I understand
correctly, it won't have any legal effect, but maybe it still helps
reduce concerns from contributors (though I haven't heard any
concerns).
Google employees can read about Google's policy at
go/releasing/contributions#copyright.
With tons of groundwork done, wee can now finally keep the index up to
date within a transaction! That means that we can start relying on the
index to always be valid, so we can use it e.g. for finding common
ancestors within a transaction. That should help speed up `jj evolve`
immensely on large repos.
We still don't write the updated index to disk when the transaction
closes. That will come later.
