On Wed, 27 Sep 2006, kfogel@tigris.org wrote:
....
> --- trunk/subversion/libsvn_ra_svn/protocol (original)
> +++ trunk/subversion/libsvn_ra_svn/protocol Wed Sep 27 12:04:02 2006
...
> +4.1. Extending existing commands
> +
> +Extending an existing command is normally done by indicating that its
> +tuple is allowed to end where it currently ends, for backwards
> +compatibility, and then tacking on a new, possibly optional, tuple.
> +For example, set-path was extended to include lock-tokens like this:
> +
> + /* OLD */ set-path:
> + params: ( path:string rev:number start-empty:bool )
> +
> + /* NEW */ set-path:
> + params: ( path:string rev:number start-empty:bool ? [ lock-token:string ] )
> +
> +The "?" says that the outer tuple is allowed to end here, because an
> +old client or server wouldn't know to send the new subtuple. The new
> +subtuple appears in square braces because, even in the new protocol,
> +the lock-token is still optional (but if there's no lock-token to
> +send, then an empty tuple must still be transmitted, so that future
> +extensions to this command remain possible). And if lock-token were
> +mandatory in the new protocol, then the braces would be parentheses
> +instead.
We probably want to indicate that optional arguments (as tuple
contents) for *new* commands need not use the "?" character before the
"(?x)" sequence, but should use that latter sequence to allow more
parameters to easily be added at the end of the command.
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Received on Thu Sep 28 04:47:37 2006