how to use delta as pager/diff tool?

[chiefjester]

Hi, 👋

I've recently used dandavison/delta/ to get better diffs.

I was wondering if there's a way to use it in the git log preview? ctrl+alt+L

I see that in fzf.vim it uses delta if it detects it's installed.

[notDavid]

Fyi for anyone else stumbling upon this and wondering why it isn’t working for them;

I’ve set delta as my pager in gitconfig, and something like git show 12345 works and will show me delta’s output.
However for some reason, when using fzf.fish “git log”, the preview window (which shows the same git show output) does not show delta’s output. I wonder why?

Anyway, setting this environment variable (in the fish shell) works for me:
set -x fzf_git_log_opts --preview='git show {1} | delta'

[kidonng]

However for some reason, when using fzf.fish “git log”, the preview window (which shows the same git show output) does not show delta’s output. I wonder why?

Because the output of git show is piped into fzf, so Git won't call the pager.

[bagohart]

The solution proposed by @notDavid works for git log, but it doesn't work for git status.
After a bit of tinkering I made it work by setting the $fzf_git_status_opts variable:
set -gx fzf_git_status_opts '--preview=fzf_preview_changed_file_using_delta {}
and adding a new function fzf_preview_changed_file_using_delta:

function fzf_preview_changed_file_using_delta
    set -l path (string split ' ' $argv)[-1]
    if string match -r '^\?\?' $argv --quiet
        echo -e (set_color --underline)=== Untracked ===\n
        _fzf_preview_file $path
    else
        if string match -r '\S\s\S' $argv --quiet
            echo -e (set_color --underline red)=== Unstaged ===\n
            git diff --color=always -- $path | delta
        end
        if string match -r '^\S' $argv --quiet
            echo -e (set_color --underline green)=== Staged ===\n
            git diff --color=always --staged -- $path | delta
        end
    end
end

That function is copied and adapted from _fzf_preview_changed_file to pipe the output of git diff through delta.

That solution is not ideal though because I will now miss updates to _fzf_preview_changed_file.

[PatrickF1]

I'm currently looking into making this a feature out of the box based on ideas from dandavison/delta#840. Stay tuned! And check out that discussion for ideas for yourself in the meantime.

[PatrickF1]

Discussed it with the git contributors here https://lore.kernel.org/git/20230816025715.GB2248431@coredump.intra.peff.net/T/#t

[PatrickF1]

Ok based on the Jeff King (the git contributor who replied) feedback, the feature I will build will read the pager command from interactive.diffFilter and if it exists, pipe the output of git show through it. So if you want to integrate your diff tool with fzf.fish, you will need to add the appropriate pager to interactive.diffFilter. Appropriate meaning it is appropriate for being in the middle of a command pipeline (e.g. it should NOT pipe to another pager).

[PatrickF1]

This has been implemented in 90a66b9! Could someone mark this as the answer please?