Prevent the sync protocol widget from over-using memory

Prevent the sync protocol widget from over-using memory

During propagation, we create a line for each file, taking memory, but
we delete all lines passed 2000 right at the beginning of the next sync.
Since the user has little chances of being able to read past those 2000
lines in the log, we might as well keep it capped at 2000 also during
propagation to prevent it from eating memory.