How to merge the changes in undofile with the current version?

Question

I use undotree to visualize the changes available in my undofile. Is it possible to merge a branch of the undofile with the current version of the file I am working on?

I am looking for something similar to merging two versions of a file in git.

Answer 1

I would:

1. Save the current version to disk
2. Select the version from the undo tree
3. Run the :Diff command

Remark: The :Diff command is not a standard Vim command but it is a common addition.

Here is the version of @romainl:

function! Diff(spec)
    vertical new
    setlocal bufhidden=wipe buftype=nofile nobuflisted noswapfile
        let cmd = "++edit #"
    if len(a:spec)
        let cmd = "!git -C " .. shellescape(fnamemodify(finddir('.git', '.;'), ':p:h:h')) .. " show " .. a:spec .. ":#"
    endif
    execute "read " .. cmd
    silent 0d_
    diffthis
    wincmd p
    diffthis
endfunction

command! -nargs=? Diff call Diff(<q-args>)