Previously, we would use `Project::serialize_buffer_for_peer` and
`Project::deserialize_buffer` respectively in the host and in the
guest to create a new buffer or just send its ID if the host thought
the buffer had already been sent.
These methods would be called as part of other methods, such as
`Project::open_buffer_by_id` or `Project::open_buffer_for_symbol`.
However, if any of the tasks driving the futures that eventually
called `Project::deserialize_buffer` were dropped after the host
responded with the buffer state but (crucially) before the guest
deserialized it and registered it, there could be a situation where
the host thought the guest had the buffer (thus sending them just the
buffer id) and the guest would wait indefinitely.
Given how crucial this interaction is, this commit switches to creating
remote buffers for peers out of band. The host will push buffers to guests,
who will always refer to buffers via IDs and wait for the host to send them,
as opposed to including the buffer's payload as part of some other operation.
Changing the frequency at which we update worktrees highlighted a
problem in the randomized tests that was causing clients to receive
a definition to a worktree *before* observing the registration of
the worktree itself. This was most likely caused by #1224 because
the scenario that pull request enabled was the following:
- Guest requests a definition pointing to a non-existant worktree
- Server forwards the request to the host
- Host sends an `UpdateProject` message
- Host sends a response to the definition request
- Server observes the `UpdateProject` message and tries to acquire
the store
- Given that we're waiting, the server goes ahead to process the
response for the definition request, responding *before*
`UpdateProject` is forwarded
- Server finally forwards `UpdateProject` to the guest
This commit ensures that, after forwarding a project request and getting a
response, we acquire a lock to the store again to ensure the project still
exists. This has the effect of ordering the forwarded request *after* any
message that was received prior to the response and for which we are still
waiting to acquire a lock to the store.
