+function s:SudaWriteUndo()
+ let p = expand('<afile>')[7:]
+ if has('win32') || !&undofile || !filereadable(p)
+ return
+ endif
+ let p = resolve(p)
+ " XXX: comments are from :help backupdir to mark implementation details
+ let x = &undodir
+ " For backwards compatibility with Vim version 3.0 a '>' at the start
+ " of the option is removed.
+ if stridx(x, '>') == 0
+ let x = x[1:]
+ endif
+ " To include a comma in a directory name precede it with a backslash.
+ for u in split(x, '\v\\@1<!,')
+ " Spaces after the comma are ignored, other spaces are considered part
+ " of the directory name.
+ let u = trim(u, ' ', 1)
+ " To have a space at the start of a directory name, precede it with a
+ " backslash.
+ if stridx(u, '\ ') == 0
+ let u = u[1:]
+ endif
+ " Empty means that no backup file will be created.
+ if empty(u)
+ continue
+ elseif u == '.'
+ " A directory "." means to put the backup file in the same
+ " directory as the edited file.
+ let d = fnamemodify(p, ':p:h')
+ elseif stridx(u, './') == 0
+ " A directory starting with "./" (or ".\" for MS-Windows) means to
+ " put the backup file relative to where the edited file is.
+ let d = printf('%s%s', fnamemodify(p, ':p:h'), expand(u))
+ else
+ let d = u
+ endif
+ " NOTE: env vars are not expanded, and backslashes are not handled...
+ if u[-2:-1] == '//'
+ let f = fnamemodify(p, ':p:gs?/?%?')
+ else
+ let f = printf('.%s.un~', fnamemodify(p, ':t'))
+ endif
+ " A directory name may end in an '/'.
+ let d = trim(d, '/', 2)
+ if !isdirectory(d)
+ continue
+ endif
+ try
+ execute printf('wundo! %s/%s', fnameescape(d), fnameescape(f))
+ break
+ catch
+ continue
+ endtry
+ endfor
+endfunction