I want to make a write-append only changelog on a replicated
store (like dropbox or gdrive)

Does anybody know if these stores handle write appends in an efficient manner.
The worse case would be that each new write append treats the new version of
the file as a totally new file and copies everything.

I have no idea if this is the case or not - does anybody know
if the entire file gets copied every time or just the increment?

If the entire file gets copied then I'd need some kind of incremental
system, create many small files, then occasionally merge them
has anybody done this?

Cheers