bug#60338: [PATCH] Add option to present server changes as diffs

[Dmitry Gutov <dmitry@gutov.dev>]

On 02/09/2023 12:55, João Távora wrote:
> Anyway I invite everyone to have a look and try to improve it, perhaps
> moving it out of Eglot into the shiny new "refactoring interface" if
> those ever become a thing.

Regarding the diff approach vs. "shiny new", I've run a little 
comparison with VS Code: doing a rename of 'glyph_row' across the Emacs 
codebase (a moderately sized project) takes about ~1.44s to produce the 
diff.

VS Code's "Refactor Preview" takes about 1/3rd of that time to show. I'm 
guessing that's because it just paints whatever the language server 
returns instead of doing a bunch of process calls. If that is the case, 
one of the approaches seems to have a fundamental performance advantage.

Not to belittle the new addition, though - it's a good step for Eglot.

Two other thoughts after trying it:

- I would probably want to bind the originally proposed 
'diff-apply-everything' to 'C-c C-c' (e.g. "commit the change to disk"), 
but that's already taken in diff-mode.

- 'git diff' has a less-frequently used option called '--word-diff' 
which could reduce the length of the diff in the case I am testing (but 
I guess diff-mode would have to be updated to support that output). And 
another way in that direction would be to reduce the size of the diff 
context (e.g. to 0).