How to write a command that uses sends the output of an arbitrary git command to fzf?

Question

I've been messing around a bit with fzf and I'd like to be able to run a command that does something like take the output of diff -w -M origin/main...HEAD --name-only and make the contents available in a preview window.

I've gotten this far, with some copy/paste from the docs:

command! -bang -nargs=* Gdomo
   \ call fzf#vim#grep(
   \   'git diff -w -M origin/main...HEAD --name-only', 0,
   \   fzf#vim#with_preview({'dir': systemlist('git rev-parse --show-toplevel')[0]}), <bang>0))

That gets me the preview window, but selecting any of the files results in:

Error detected while processing function 24[30]..<SNR>53_callback[23]..function 24[30]..<SNR>53_callback:
line   21:
Vim(let):E684: list index out of range: 1

I'm guessing that trying to wrap grep is my first mistake, but I've looked at the plugin code and it's not clear to me what a better approach would be.

Answer 1

It turns out I was overthinking this and I also missed some of the documentation. fzf#run can accept an arbitrary command which returns a list of files.

A working example without a preview window:

command! GDomo
  \ call fzf#run({'source': 'git diff -w -M origin/main...HEAD --name-only', 'sink': 'e'})

A working example with a preview window:

command! GDomo
  \ call fzf#run(
  \   fzf#vim#with_preview(
  \     fzf#wrap({ 'source': 'git diff -w -M origin/main...HEAD --name-only' })
  \   )
  \ )

Answer 2

Thanks to @oalders.

I created an unrestricted find files command using fd, please checkout this issue: https://github.com/junegunn/fzf.vim/issues/1454

Here's the source code:

    command! -bang -nargs=? -complete=dir UnrestrictedFiles
        \ call fzf#run(
        \   fzf#vim#with_preview(
        \     fzf#wrap({ 'source': 'fd -tf -tl -i -u --exclude ".git" '.shellescape(<q-args>) }, <bang>0)
        \   )
        \ )