With this patch, we auto-upgrade existing repos that use Thrift format
for the operation log to use Protobuf format. That would only be repos
used with an unreleased version of jj after 0.5.1 (which may be the
majority of repos?).
The upgrade from Thrift is simpler because we now use the same hashing
scheme for the Protobuf-based storage, so the operation and view IDs
remain the same as they were in the Thrift-based storage. We could
simplify the code a bit more as a result, but since this code is
supposed to be short-lived, I didn't bother.
Since the change from the Protobuf format with the old hashing scheme
to a the (same) Protobuf format with the new hashing scheme shouldn't
impact users, I removed the entry we had in the changelog about the
format change.
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.
As mentioned in the previous commit, we need to remove the Protobuf
dependency in order to be allowed to import jj into Google's
repo. This commit makes `SimpleOpStore` store its data using Thrift
instead of Protobufs. It also adds automatic upgrade of existing
repos. The upgrade process took 18 s in my repo, which has 22k
operations. The upgraded storage uses practically the same amount of
space. `jj op log` (the full outut) in my repo slowed down from 1.2 s
to 3.4 s. Luckily that's an uncommon operation. I couldn't measure any
difference in `jj status` (loading a single operation).
In order to allow building jj inside of Google, our Protobuf team
doesn't want to us to use a Google-unsupported implementation. Since
there is no supported implementation in Rust, we have to migrate off
of Protobufs. I'm starting with the operation store. This commit moves
the current implementation to a separate file so it can easily be
disabled by a Caargo feature.
