[[!comment format=mdwn
 username="joey"
 subject="""comment 1"""
 date="2015-08-04T20:19:22Z"
 content="""
`git annex sync --content` does what you want, only it also does a pull and
a merge from remotes.

I don't know that wanting to only push, w/o pull and merge, is common
enough to make a separate command for it.

There's also the problem that to push the git-annex branch, it really
makes sense to first pull/merge from the remote. Otherwise, the push
is not likely to work as well. And too, it makes sense to update the
git-annex branch from remotes in order to know what files that have, so
that info can be better used to decide which files to send to them --
especially when preferred content might make some file not be sent to all
remotes, depending on which other remotes contain the file.
"""]]