Select candidate if it's multi lines?

[tmpm697]

Checklist

• [X] I have read through the manual page (man fzf)
• [X] I have searched through the existing issues
• [X] For bug reports, I have checked if the bug is reproducible in the latest version of fzf

Output of fzf --version

0.53

OS

• [ ] Linux
• [X] macOS
• [ ] Windows
• [ ] Etc.

Shell

• [X] bash
• [X] zsh
• [ ] fish

Problem / Steps to reproduce

Say I have a list candidates of mixed one line and multi lines (multi lines ended with NUL char),

declare -f |
  perl -0 -pe 's/^}\n/}\n\0/gm' |
  bat --plain --language bash --color always |
  fzf --read0 --ansi --layout reverse --multi --highlight-line

Output of declare -f is a mixed of one line and multi lines candidates.

How to check focus line while running fzf, to see if it's multi lines or not, if yes then select it?

[tmpm697]

https://github.com/junegunn/fzf/issues/3901