[picker.git_diff] preview truncate output from diff

[robsonjorgefernandez]

Hi to everyone!

I'm encountering an issue where using <leader>gf truncates the preview, displaying only the currently visible lines on preview pane rather than the full diff content.

map("n", "<leader>gf", function() Snacks.picker.git_log_file() end, { desc = "Git Current File History" })

picker = {
  layout = {
    preset = "wide",
  },
  layouts = {
    wide = {
      layout = {
        width = 0.95,
        height = 0.95,
        box = "vertical",
        border = true,
        title = "{title} {live} {flags}",
        title_pos = "center",
        { win = "input", border = "bottom", height = 1 },
        { win = "list", border = "none", height = 10 },
        { win = "preview", title = "{preview}", border = "top" },
      },
    },
  },
  previewers = {
    diff = {
      style = "terminal",
      cmd = { "hunk", "pager",  "--mode", "split" },
     --- cmd = { "delta" }
    },
  },
}

If I use style = "fancy", it works with no problem. However, this mode doesn't have a side-by-side option. So, I'm trying to use delta or hunk instead.

My gitconfig:

[core]
  editor = nvim
  excludesfile = ~/.gitignore
  pager = "hunk pager --mode split"
  ; pager = delta

When I scroll down, nothing appears after line 179.

But on lazygit or git diff there are more content:

❯ git diff 26d0983 HEAD -- configs/home/.config/nvim/lua/plugins/snacks.lua | wc -l
172

Any ideia?

[drowning-cat]

Related:

• How to have git_diff look the same as terminal output #2471 (reply in thread)

[drowning-cat]

@robsonjorgefernandez

How do you expect to scroll the picker preview when it's displaying a terminal buffer in Normal mode?

You're using an interactive terminal program to display hunks. hunk pager doesn't return the full output. Instead, it spawns a process that expects you to interact with it by pressing keys inside the terminal. So, if you want to scroll inside hunk pager, you need to focus the preview and enter Terminal mode. As shown in the example below, you can also send keys directly to the terminal process.

Note

Focus the preview (<M-w> twice) and press a to enter Terminal mode (i is already used by the focus_input action).

Tip

If you'd rather enter Terminal mode automatically whenever the preview gains focus, here's a workaround:

vim.api.nvim_create_autocmd({ "BufEnter", "WinEnter" }, {
  desc = "Automatically enter Terminal mode when focusing the snacks preview",
  pattern = "term://*",
  group = vim.api.nvim_create_augroup("preview_insert_term", {}),
  callback = function()
    vim.schedule(function()
      for _, picker in ipairs(Snacks.picker.get()) do
        if picker:current_win() == "preview" and vim.bo.buftype == "terminal" then
          vim.cmd.startinsert()
        end
      end
    end)
  end,
})

Configure scrolling:

---@module 'snacks'

return {
  "folke/snacks.nvim",
  ---@type snacks.Config
  opts = {
    picker = {
      sources = {
        git_log_file = {
          previewers = {
            diff = {
              -- NOTE: We assume `hunk pager` is used as the default git pager
              style = "terminal",
            },
          },
          actions = {
            term_ins = function(picker)
              local mode = vim.api.nvim_get_mode().mode
              if vim.bo.buftype == "terminal" and mode ~= "t" then
                vim.cmd.startinsert()
              else
                picker:action("focus_input")
              end
            end,
            term_exit = function(picker)
              local mode = vim.api.nvim_get_mode().mode
              if vim.bo.buftype == "terminal" and mode == "t" then
                vim.cmd.stopinsert()
                vim.api.nvim_input("0")
              else
                picker:action("close")
              end
            end,
            hunk_pager_scroll_down = function(picker)
              local chan = vim.bo[picker.preview.win.buf].channel
              if chan ~= 0 then
                vim.api.nvim_chan_send(chan, "<C-f>")
              end
            end,
            hunk_pager_scroll_up = function(picker)
              local chan = vim.bo[picker.preview.win.buf].channel
              if chan ~= 0 then
                vim.api.nvim_chan_send(chan, "<C-b>")
              end
            end,
          },
          win = {
            input = {
              keys = {
                ["<C-f>"] = { "hunk_pager_scroll_down", mode = { "i", "n" } },
                ["<C-b>"] = { "hunk_pager_scroll_up", mode = { "i", "n" } },
              },
            },
            preview = {
              keys = {
                ["i"] = { "term_ins", mode = { "t", "n" } },
                ["<Esc>"] = { "term_exit", mode = { "t", "n" } },
              },
            },
          },
        },
      },
    },
  },
}

[dpetka2001]

Snacks.picker.git_log_file essentially just shows the diff for the specific commit and the specific file.

Your git diff 26d0983 HEAD -- configs/home/.config/nvim/lua/plugins/snacks.lua shows the diff between the specific commit and HEAD. Didn't test Lazygit but I'm assuming it's doing the same, except if you pass it some options to only show the diff for the file for the specific commit only.

So you should compare the output of Snacks.picker.git_log_file with the command git diff 26d0983^! -- configs/home/.config/nvim/lua/plugins/snacks.lua

[drowning-cat]

{ "git", "show", "<hash>", "--", "<file>" }

Note

previewers.diff.cmd does not affect the pager command used by git_log_file. In this case, the pager is configured through ~/.gitconfig.

snacks.nvim/lua/snacks/picker/config/sources.lua

Line 418 in 882c996

preview = "git_show",

snacks.nvim/lua/snacks/picker/preview.lua

Lines 244 to 254 in 882c996

	---@param ctx snacks.picker.preview.ctx
	function M.git_show(ctx)
	local cmd, terminal = git(ctx, "show", ctx.item.commit)
	local pathspec = ctx.item.files or ctx.item.file
	pathspec = type(pathspec) == "table" and pathspec or { pathspec }
	if #pathspec > 0 then
	cmd[#cmd + 1] = "--"
	vim.list_extend(cmd, pathspec)
	end
	M.cmd(cmd, ctx, { ft = not terminal and "git" or nil })
	end

[dpetka2001]

Yes, but that still does not invalidate what I said in terms of the command comparison based on OP's post. He should not compare what's shown in preview with git diff some_commit_sha HEAD. The latter shows the diff for all commits from commit_sha up to HEAD for a pathspec. In preview only git show commit_sha for a specific pathspec is shown.

I compared in the local snacks repo and they both show the same lines. Did not test lazyit. Just pure git commands with what git_log_file previewer shows. In my .gitconfig I just had

[core]
  pager = delta
[delta]
  paging = always
  side-by-side = true

[drowning-cat]

Yes, but that still does not invalidate what I said

Yep, sorry. I only got it after your second message. Basically, the OP is comparing all changes between the selected commit and HEAD (N commits), instead of just the changes introduced by that commit.

side-by-side = true

Nice tip.

[dpetka2001]

No need for sorry. I don't get offended by you after all the exchanges we've had 😄

Just wanted to clarify what OP compares.

[robsonjorgefernandez]

Sorry for the delay, guys!

Maybe I phrased that wrong, but what I'd like to achieve is using style = "terminal" while still being able to scroll up/down with <C-f> and <C-b> to see all the changes.

I made this video to show you what's happening.

01.mp4

As you can see, I don't have this issue with the fancy style, but that's not the case when I try using delta.

Note

<C-f> is my leader key on wezterm, because of that I need to press twice.

System Details for Context

❯ nvim --version
NVIM v0.12.4
Build type: Release
LuaJIT 2.1.1774638290
Run "nvim -V1 -v" for more info

❯ delta --version
delta 0.19.2

❯ git --version
git version 2.55.0

● LazyVim 5.57ms  start
    dir     /home/robson/.local/share/nvim/lazy/LazyVim
    url     https://github.com/LazyVim/LazyVim
    version 16.0.0
    tag     v16.0.0
    branch  main
    commit  c10948c
    readme  README.md
    help    |LazyVim.txt|
    
● Operating System: Fedora Linux 44 (Workstation Edition)    

[dpetka2001]

First again you're comparing the output with git diff. That's not correct.

You should compare the output with git show of Snacks.picker.git_log() and Snacks.picker.git_log_file().

You should compare the output of git diff with Snacks.picker.git_diff(). Also do mind that if you want to see the whole changes like git diff then Snacks.picker.git_status() is what you want. Snacks.picker.git_diff() will show the diff chunks. As you can see in the screencast attached below it shows the 2 hunks in bufdelete.lua file as 2 entries. Snacks.picker.git_status() shows it like it shows in git diff with delta enabled.

This is how it looks for me on Windows.

07.08.2026_14.09.46_REC.mp4

All looks fine to me from my testing. I would guess that it's some option of delta that interferes. Try commenting out all options from delta except paging and side_to_side (I only have those enabled in my gitconfig) and test again.

[robsonjorgefernandez]

First again you're comparing the output with git diff. That's not correct.

The idea of running git diff in the CLI was simply to show the diff outside of nvim .

However, the problem to my issue was the parameter delta.pager = "nvimpager -a":

❯ nvimpager -h
Usage: nvimpager [-acp] [--] [nvim options and files]
       nvimpager -h
       nvimpager -v

nvimpager provides a simple pager based on neovim.
Options:
  -h            this help
  -v            version output
  -a            enforce auto mode (default)
  -c            enforce cat mode
  -p            enforce pager mode

Changing to nvimpager -c or comment it, solve my issue.

Thank you for leading me to the right spot and attention to this issue.

May I ask another question related to the preview?
I don't know if you noticed in my video (at 1:55), but my preview wasn't using the correct screen width. That's why I need to pass the width parameter like this:

cmd = { "delta", "--width", math.floor(vim.api.nvim_win_get_width(vim.api.nvim_get_current_win()) * 0.9) }

Is this the right/common way to solve it?

[dpetka2001]

You can also pass to your .gitconfig the value delta.width = 230 for example, but that will be hardcoded and if you resize the window the formatting might get weird because delta will still try to output based on the width of gitconfig. So, I think the best solution is to calculate the width from inside Neovim like you did in cmd.