bug#62426: [PATCH] eshell: Add 'rgrep' builtin.

[Jim Porter]

On 3/24/2023 2:02 PM, Antero Mejr via Bug reports for GNU Emacs, the 
Swiss army knife of text editors wrote:
> eshell has builtins for agrep/egrep/fgrep that use the Emacs grep
> feature, but rgrep is not included so it behaves differently. This patch
> adds the rgrep builtin.

Thanks, I think it would make sense to add an rgrep built-in to Eshell. 
However, I'm not sure if this is the best way for it to work. 
Personally, I'd have expected this to use the 'rgrep' function in Emacs 
Lisp (which uses find + grep to do its job). That's a bit different from 
/usr/bin/rgrep, but I find it a lot more useful since it ignores 
"uninteresting" files by default. For example, 'M-x rgrep' in a Git repo 
ignores the .git/ subdir, but /usr/bin/rgrep includes that subdir. 
Hence, I'd almost always prefer Emacs' version of rgrep.

That said, it might be a bit strange for Eshell's rgrep to work this 
way, when Eshell's agrep/egrep/fgrep work like the external versions. 
This seems like a tricky case...