I can reproduce this.

I dug around a little bit while I don't really have a solution, my instinct is telling me that that command is not very well suited for passing the output through pipes. At least not with how telescope currently works.

I played around with this bit of code. If you do as well, you should see that, for you command, after the first stdout chunk, each subsequent chunk appears to start with a new line. The telescope code doesn't handle that well. Try it with the original command, the new line comes after the chunk is done. Maybe the telescope code should handle this better, but also maybe git is being weird.

local uv = vim.loop
local stdin = uv.new_pipe()
local stdout = uv.new_pipe()
local stderr = uv.new_pipe()

local handle, pid = uv.spawn("git", {
	args = {
		"log",
    -- "--pretty=oneline",
    -- "--abbrev-commit",
		"--date=format:%y/%m/%d",
		"--pretty=format:%h %ad %s",
		"--follow",
		"/tmp/testing/dotfile/nvim/.config/nvim/lua/plugins/telescope.lua",
	},
	stdio = {
		stdin,
		stdout,
		stderr,
	},
}, function(code, signal) -- on exit
	print("exit code", code)
	print("exit signal", signal)
end)

print("process opened", handle, pid)

stdout:read_start(function(err, data)
	assert(not err, err)
	if data then
		vim.print("stdout chunk", data)
	else
		vim.print("stdout end")
	end
end)

Thanks for your instinct, I find a workround to solve this issue.

I create a bash script named gitlog.sh to output all content of git log in one time, so the content passed to Telescope will be processed only once, it works as my wish!

This is my script:

#!/usr/bin/env bash

# $1 is the file path from Telescope
git log --date="format:%y/%m/%d" --pretty="format:%C(auto) %h %ad %s" --follow $1 >/tmp/gitlog && cat /tmp/gitlog

And this is my Telescope config

    config = function()
        local bufopts = { noremap = true, silent = true }
        local builtin = require("telescope.builtin")
        vim.keymap.set("n", "gb", function()
            builtin.git_bcommits({
                git_command = { "/location/of/gitlog.sh" },
            })
        end, bufopts)
        vim.keymap.set("n", "gj", builtin.git_bcommits, bufopts)

        require("telescope").setup({})
    end,

@jamestrew Do you think it's necessary to keep this issue open and let's work through it to solve the problem once and for all, or do we just stop here, there's already a workround anyway, after all not all bugs have to be fixed and it's not necessarily a Telescope's bug

I think it's ok to leave it open. This might be something worth looking into deeper.

Thanks for your instinct, I find a workround to solve this issue.

I create a bash script named gitlog.sh to output all content of git log in one time, so the content passed to Telescope will be processed only once, it works as my wish!

This is my script:

#!/usr/bin/env bash

# $1 is the file path from Telescope
git log --date="format:%y/%m/%d" --pretty="format:%C(auto) %h %ad %s" --follow $1 >/tmp/gitlog && cat /tmp/gitlog

And this is my Telescope config

    config = function()
        local bufopts = { noremap = true, silent = true }
        local builtin = require("telescope.builtin")
        vim.keymap.set("n", "gb", function()
            builtin.git_bcommits({
                git_command = { "/location/of/gitlog.sh" },
            })
        end, bufopts)
        vim.keymap.set("n", "gj", builtin.git_bcommits, bufopts)

        require("telescope").setup({})
    end,

I tried your workaound, but I still get an empty window. However if I replace what’s inside of the gitlog.sh file with

git log --follow $1 >/tmp/gitlog && cat /tmp/gitlog

then I do get the result of git log in my telescope popup …

EDIT: If I just add an echo "" >> /tmp/gitlog command in the end it works

¯\_(ツ)_/¯

So the workaround becomes

git log --date="format:%y/%m/%d" --pretty="format:%C(auto) %h %ad %s" --follow $1 \
  >/tmp/gitlog \
  && echo "" >> /tmp/gitlog \
  && cat /tmp/gitlog