The accepted answer requires you to specify which buffers will receive the diff. From your question wording, it sounds like you want to push a change to every other buffer (e.g. if you had 10 diff buffers -- after recompiling vim -- you'd need to diffput to buffers 1,2,3,4,5,6,7,8,9)
I use the following to push to all buffers:
function! GetDiffBuffers()
return map(filter(range(1, winnr('$')), 'getwinvar(v:val, "&diff")'), 'winbufnr(v:val)')
endfunction
function! DiffPutAll()
for bufspec in GetDiffBuffers()
execute 'diffput' bufspec
endfor
endfunction
command! -range=-1 -nargs=* DPA call DiffPutAll()
and then just run :DPA
to push to all buffers.