server: Added support for n_predict values of -2

[N0rthHXD]

fixes issue #12264

Added support for n_predict values of -2.
n_predict = -2 this parameter ensures that n_predicts is the context length, but it is not implemented.

[ngxson]

Maybe duplicate of #12323 ?

[N0rthHXD]

Maybe duplicate of #12323 ?

I think #12323 lacking some judgment logic, and n_ctx error by @ggerganov's review. If you think it is a duplicate, I can communicate my algorithm and close the PR.

[N0rthHXD]

https://github.com/ggml-org/llama.cpp/pull/12323/files#:~:text=if%20((params.,%7D
if global_params.n_predict == 16, params.n_predict = -2, this logic will return false, that's error.

[ngxson]

Tbh this n_predict == -2 is just too messy, as we have no notion of global value or request value is more prioritized.

I personally want to remove it since we already had --no-ctx-shift that does the same thing, cc @ggerganov too

[ggerganov]

I personally want to remove it since we already had --no-ctx-shift that does the same thing, cc @ggerganov too

Makes sense. Let's remove it to make things simpler.

[N0rthHXD]

n_predict == -2 is messy indeed.

[ngxson]

superseded by #12364