Can I pass multiple arguments to grepprg?

Nobody has claimed this yet.

I know we can pass the `$*`(the grep text) to `grepprg`, but can we also specify the root-directory I want to grep from? i.e.

```vim
let g:grepper = {
\ 'grep': {
\ 'grepprg': 'grep -Rn arg0_grep_text arg1_the_folder'
\ },
\ 'tools': ['grep']
\}
```

Then in vim:
```bash
:Grepper -tool grep -quickfix -highlight
# in prompt
grep -Rn arg0_grep_text arg1_the_folder> my-text-for-grep my-folder-path-for-grep
```

The `arg1_the_folder` really matters when your project too big and u need to limit the result in a given folder.

Start by reading how grepprg is handled in the :Grepper prompt flow, especially how the grep text is passed to the configured command. Confirm that the prompt can preserve both the search text and a root-folder argument, then verify that the resulting grep command limits results to that folder.

Written by the indexing model from the issue text.