bug#70036: 30.0.50; Move file-truename to the C level

[Felician Nemeth]

Theodor Thornhill <theo@thornhill.no> writes:

> This wouldn't help for the usage in find-buffer-visiting, though. But
> this one could more easily be replaced by reworking the diagnostics
> handler. We could store the last received diagnostics in the server
> object, and do a quick lookup from known buffers there.

eglot-handle-notification:textDocument/publishDiagnostics,
eglot--xref-make-match, and eglot--apply-workspace-edit call
find-buffer-visiting.  It seems to me only the first case might be
really time sensitive.  Theo, can you email me the relevant messages
that your server sends to Emacs?  Does the server send lots of similar
diagnostics messages frequently?

Thanks,
Felicián