Previously, if the client was disconnected while the initial worktree
state was being sent, it would not see the remaining state after reconnecting.
This was due to `scan_id` and `completed_scan_id` both being initialized to
`0`, so the client would ask for updates since `0` and get nothing.
This commit changes the worktree to initialize `scan_id` to `1` and
`completed_scan_id` to `0`, so that we get the full worktree again on reconnect.
Antonio Scandurra
5eb1719ab8