Mapping keys only in diff mode

[tommyalatalo]

I'm trying to map keys for vim-fugitive that are only active in diff mode, but I wasn't able to find any examples of how to approach this in the lazy docs.

Specifically what I'm trying to do is to map <leader>n to run :diffget //3 when in diff mode, and I found the example seen below of another mapping on stackoverflow showing how to check for the diff mode. But I'm not sure if this kind of expression is possible with the keys config for the plugin, or if it needs to be done some other way?

nnoremap <expr> <C-J> &diff ? ']c' : '<C-W>j'

[dpetka2001]

Not 100% if it'll work but maybe you could try in the config function of vim-fugitive spec the following

if vim.wo.diff then
	vim.keymap.set("n", "<leader>n", "<cmd>diffget //3<cr>", { desc = "whatever you want" })
end

[tommyalatalo]

Thanks for the suggestion, I tried this but unfortunately it didn't work.