A slightly off-the-wall approach might be to have the submitting machine create the diff and send it along with the main package. The server is relieved of having to worry about it at a probably small cost in network usage.

Another option - don’t send the whole diff out by email; save it to somewhere that has a stable URL and put that in the email. 

tim
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tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
Strange OpCodes: RIW: Re-Invent Wheel