feat(defaults): use ripgrep (rg) for 'grepprg' if available

[LunarLambda]

Discussed as an idea in #28296.

Changes the defaults for 'grepprg' and 'grepformat' to use ripgrep and its --vimgrep mode, if available on the system.

Points discussed in the thread:

• Zero configuration: This PR provides a better default for an existing vim feature (:grep), which the user is free to configure themselves as needed. It adds no additional configuration settings or hooks.
• Low to zero maintenance: The change consists of a single executable() check and two option changes. It is very unlikely that ripgrep will experience breaking changes in its CLI that would necessitate adjusting the code or adding version checking.
• Performance: A basic benchmark (running a recursive, fixed string search on the neovim repository) shows significant performance improvements over GNU grep (few seconds vs <1 second).
• Precedence: Many popular plugins already integrate with ripgrep for searching, and ripgrep itself provides features specifically for integrating with vim (--vimgrep format, --smart-case option). This makes it a promising candidate for a place where Neovim can match the pulse of the community.

This is my first PR to adjust core Neovim code, as such there's a few points I am seeking feedback on:

• Is this change wanted? The discussion thread concluded that the change is promising, but may not be wanted by Neovim users.
• Is the documentation appropriate? I Added a small note to the documentation of 'grepprg' that points the user toward ripgrep and why they may want to use it. Is it clear enough that this default only takes effect if the user makes sure that the rg binary is found by Neovim?
• Does this need extra testing? @clason mentioned a :checkhealth test, I'm unsure what that should look like.

I'm happy to make any necessary adjustments.

[clason]

a :checkhealth test, I'm unsure what that should look like.

I would recommend a new section on "optional tools" that checks vim.fn.executable('rg') == 1 and prints OK if so and WARN if not. Bonus points for adding

• which rg and
• rg --version

output. (We can extend this later with curl and git and tree-sitter, once we use them.)

[LunarLambda]

Have adjusted the documentation, turned off the default filtering (with a note in the documentation hinting the user they may want to re-enable it if they wish), and added a rudimentary healthcheck.

[LunarLambda]

I have overhauled the documentation as requested. I've kept the health check in the proposed 'External Tools' section for now.

[clason]

Needs a news.txt (and probably also vim-diff.txt) entry.

[LunarLambda]

Needs a news.txt (and probably also vim-diff.txt) entry.

For vim-diff, which section? nvim-defaults? Is a single line calling out grepprg sufficient?

For news.txt, is this news-breaking or news-changed (or news-features, even) ? Is there a specific ordering to those sections or should it simply go at the end?

[clason]

For vim-diff, which section? nvim-defaults? Is a single line calling out grepprg sufficient?

I'd say nvim-defaults

For news.txt, is this news-breaking or news-changed (or news-features, even) ? Is there a specific ordering to those sections or should it simply go at the end?

I'd say to the "Defaults:" list under news-changed (at the end).

[LunarLambda]

Added. For the sake of brevity I did not include the full default value, since both places link to the option where it's documented.

[LunarLambda]

Happy to have landed this! Thank you for the feedback and advice.

[dundargoc]

Thanks for this! The PR description and the context is useful, be sure to add that to the commit message as well next time :)

[gpanders]

Apologies for the late review, but what is the rationale for -uuu rather than -uu? Is this strictly for compatibility with grep (which also searches binary files by default)?

Omitting binary file matches strikes me as a better default for a text editor. If the concern is consistent behavior for both rg and grep, I'd suggest adding -I to the default grepprg to ignore binary file matches in all cases.

[LunarLambda]

yes rg -uuu matches grep -r. I do agree that omitting binary files would be better. The documentation at least points out that the user may wish to adjust the flags used

[gpanders]

The use of /dev/null here is also unnecessary AFAIK. It's used for grep because some versions of grep (e.g. BSD grep) will try to read from stdin if no file argument is given, so a plain grep foo will block indefinitely and the /dev/null argument prevents that.

But ripgrep does not behave that way, and adding /dev/null here means you cannot use :grep foo to search for foo recursively (since that expands to rg -uuu foo /dev/null, which of course returns nothing).

[LunarLambda]

ripgrep searches the current directory by default. given it's also recursive by default, the /dev/null placeholder is to be both consistent with regular grep, and to prevent an accidental grep without files from potentially spinning up a lengthy process.

[LunarLambda]

Given the feedback by @gpanders, is it worthwhile to revisit this before 0.10? Either when #23235 is closer to completion, or I could do it this weekend. The change is still very young, so I don't think many people have seen or given feedback on it yet, but I do think the suggestions are worth considering.

[clason]

Sure, can still be changed (but also in a 0.10.x, so not a blocker either way).