mini.diff config for jujutsu

[farnoy]

Sharing in case someone finds it useful. Should work with multiple repos/workspaces. Doesn't have hunks since those don't make sense with jj. Uses --ignore-working-copy so it should pollute your oplog.

local cache = {}

local function get_buf_realpath(buf_id)
  return vim.loop.fs_realpath(vim.api.nvim_buf_get_name(buf_id)) or ''
end

local function repo_dir(path)
  local result = vim.system({ 'jj', '--ignore-working-copy', 'root' }, { cwd = vim.fs.dirname(path) }):wait()
  if result.code == 0 then
    return vim.trim(result.stdout)
  else
    return nil
  end
end

local function invalidate_cache(buf_id)
  local cache = cache[buf_id]
  if cache == nil then return false end
  pcall(function()
    cache.fs_event:stop()
    cache.timer:stop()
  end)
  cache[buf_id] = nil
end

local function start_watching(buf_id, path)
  local repo = repo_dir(path)
  if repo == nil then return false end
  local watchfile = vim.fs.joinpath(repo, ".jj/working_copy")

  local buf_fs_event, timer = vim.loop.new_fs_event(), vim.loop.new_timer()
  local set_ref_text = function()
    vim.system(
      { "jj", "--ignore-working-copy", "file", "show", "-r", "@-", "\"" .. path .. "\"" },
      { cwd = vim.fs.dirname(path), text = true },
      vim.schedule_wrap(function(res)
        local MiniDiff = require('mini.diff')
        MiniDiff.set_ref_text(buf_id, res.stdout)
      end)
    )
  end

  local watch_index = function(_, filename, _)
    if filename ~= "checkout" then return end
    timer:stop()
    timer:start(50, 0, set_ref_text)
  end
  buf_fs_event:start(watchfile, { recursive = true }, watch_index)

  invalidate_cache(buf_id)
  cache[buf_id] = { fs_event = buf_fs_event, timer = timer }

  set_ref_text()
end

return {
  {
    "echasnovski/mini.diff",
    opts = {
      source = {
        name = "jj",
        attach = function(buf_id)
          if cache[buf_id] ~= nil then return false end

          local path = get_buf_realpath(buf_id)
          if path == '' then return false end

          return start_watching(buf_id, path)
        end,
        detach = function(buf_id)
          invalidate_cache(buf_id)
        end,
      }
    }
  }
}

[echasnovski]

That's very nice! Thanks for sharing!

The only issue I spotted is quite minor: I don't think local set_ref_text needs vim.schedule_wrap, as vim.system callback already has vim.schedule_wrap. But I might be wrong here.

---

I do have aspirations to look one day into adding built-in sources for alternative VCS (jujutsu, mercurial, fossil). If 'mini.diff' design is extensible, might as well make it easier to leverage. Just at the moment I don't think the payoff is worth the work (code+tests+docs) and increasing 'mini.diff' size. Some day.

[farnoy]

Thanks for pointing that out. You're right, the double wrap is unnecessary, it was a leftover from when I had logging there. Updated the post

[sivansh11]

@farnoy, do you have any idea how someone would use mini.diff for jj split/resolve ?
Both are quite involved actions

[farnoy]

I used this for a while, but there were some blockers and I went back to :builtin