If the client wants x,y and starts out by saying have F,S, the server
doesn't know what F,S is. Eventually the client says "have d" and
the server sends "ACK d continue" to let the client know to stop
-walking down that line (so don't send c-b-a), but its not done yet,
+walking down that line (so don't send c-b-a), but it's not done yet,
it needs a base for x. The client keeps going with S-R-Q, until a
gets reached, at which point the server has a clear base and it all
ends.
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If the server sends back the 'delete-refs' capability, it means that
-it is capable of accepting an zero-id value as the target
+it is capable of accepting a zero-id value as the target
value of a reference update. It is not sent back by the client, it
simply informs the client that it can be sent zero-id values
to delete references.