File changed [+] indicator for statusline

Question

In both the plugins I use for Vim and neovim statuslines, an indicator shows that the file has been changed since it was last saved. It looks like this on one of them after the current buffer filename: [+]. I think it's handy to show where you started when repeatedly undoing changes with u.

I don't use a statusline plugin on gVim as I prefer to keep it as plain-looking as possible, but I keep missing that indicator. Is there a function that I can use to add it?

This is my current statusline gVim configuration:

set statusline=
set statusline+=%f
set statusline+=%=
set statusline+=%l:%c\ \ %p%%
hi StatusLine guibg=grey70 guifg=#eeeeee

Answer 1

Pointer in the comments led me to add this after the filename and it does exactly what I wanted. The \ is to add a space between the filename and the indicator.

set statusline+=\ %m