Make streaming not repeatedly insert the same thing

[ultronozm]

• llm.el (llm-chat-streaming-to-point): Ignore common prefix between streamed text and buffer contents.

The motivation is as follows: without this patch, when the streamed text gets long enough, the call to (delete-region start end) (insert text) causes the buffer position to reset, preventing the user from viewing parts of the buffer away from the stream. Happy to clarify or illustrate if that would help.

[ahyatt]

Thanks - I think this makes sense! Would you mind adding a comment in the code about the motivation for doing this?

Also, have you done FSF copyright assignment yet? No issues either way, but if you haven't, we need to make sure your total contribution to the project doesn't exceed about a dozen lines.

[ultronozm]

Thanks, comments added. Yes, I'm all set re. FSF.

By the way, it wasn't clear to me the reason for passing the accumulated string to llm-chat-streaming-to-point (rather than the new part). Is this because the chunks could conceivably arrive out of order, or something else?

[ahyatt]

I felt like both passing the accumulated version, or the complete string, could make sense, but felt that the complete string might be more useful. I didn't want the clients to have to store the accumulated string.

Thanks for the change!