Custom merge tool like vimdiff1?

[heygarrett]

I'm trying to set up a custom merge tool that works like vimdiff1:

"$merge_tool_path" -f -d \
	-c 'echon "Resolve conflicts leftward then save. Use :cq to abort."' \
	"$LOCAL" "$REMOTE"

The problem is this, from the Jujutsu docs linked above:

$output (REQUIRED) is replaced with the name of the file that the merge tool should output. jj will read this file after the merge tool exits.

But $output contains both sides of the conflict as well as the conflict markers (or is otherwise empty).

Is there a way to do something like this?

[merge-tools.nvim]
program = "nvim"
merge-args = [
	"-f", "-d",
	"$left", "$right",
]

I only want $left and $right when resolving the conflict, and I want the contents of $left to be the file that jj reads after the merge tool exits.

[bnjmnt4n]

You could write a custom shell script wrapper which invokes nvim with only the $left and $right arguments, then copies the contents of the $left file to $output. Perhaps something like the following (untested):

[merge-tools.nvim]
program = "nvim-wrapper.sh"
merge-args = ["$left", "$right", "$out"]

#!/bin/sh
nvim -f -d $1 $2
cp $1 $3

[heygarrett]

Oh, that's what the second part of vimdiff1 is doing. 🤦‍♂️

Okay, this works. I wonder, though, if it would be possible to store this as a jj alias instead of a separate shell script. 🤔

[heygarrett]

Actually, I think I found another, albeit slightly different, way to do this with a Neovim command:

[merge-tools.nvimdiff]
program = "nvim"
merge-args = ["-c", "JJdiff", "-d", "$left", "$output", "$right"]

vim.api.nvim_create_user_command("JJdiff", function()
	local left_contents = vim.api.nvim_buf_get_lines(0, 0, -1, true)
	-- close $left
	vim.cmd.diffoff()
	vim.cmd.close()
	-- put contents of $left into $output
	vim.api.nvim_buf_set_lines(0, 0, -1, true, left_contents)
end, { desc = "jj diff setup" })

[heygarrett]

Thank you for your help, @bnjmnt4n!