Use gina as merge tool

[amikai]

Accroding https://www.grzegorowski.com/using-vim-or-neovim-nvim-as-a-git-mergetool,
vim can use vim-fugitive as git mergetool by following git config.
How to use gina like this?

# define command which will be used when "nvim" is set as a merge tool
[mergetool "nvim"]
  cmd = nvim -f -c \"Gdiffsplit!\" \"$MERGED\"
# set "nvim" as tool for merging
[merge]
  tool = nvim
# automatically launch merge tool without displaying a prompt
[mergetool]
  prompt = false

[lambdalisue]

I've never used git's mergetool itself thus I've no idea. Help wanted.