VIM function to save the selected range to a file and replace the contents with a pointer to the file. Goot to be used with http://github.com/urubatan/codemerger

gistfile1.vim

function! ExtractText(fileName,first_line,last_line)
    let text = getline(a:first_line,a:last_line)
    execute ":" . a:first_line . "," . a:last_line . "delete"
    execute "normal O{{" . a:fileName . "}}"
    return writefile(text, a:fileName)
endfunction
command! -range -nargs=1 Es call ExtractText(<f-args>,<line1>,<line2>)

Forgot to say, to use it, select visually a range :Es newFileName