Easy Non-Fast-Forward Pushes

As far as I understand, a push will always modify (or add) a ref in the remote repository. When pushing to branch B, then the ref pointing to the last commit in this branch will be moved, provided that this can be done in a fast-forward way. Otherwise the push will fail.

The following options exist:

(1) force the push (2) fetch, merge, then push (3) push to a different branch

I don't want (1), for obvious reasons.

Option (2) implies that a particular person has to do the merge, namely the
person for whom the push is failing, or in other words: the person
unfortunate enough not being the first to push. (This reminds me of
Subversion: whoever tries to commit after someone else has committed will
have the burden of an update and possible merge.)

Option (3) allows others to recognize the situation, and anyone with repository access can do a merge. This is a good thing. However, I am confused as to what branch name should be used for this. In Mercurial, we would say that a new "head" is created, and anyone can recognize this by using "hg heads" and do a merge if he feels competent enough. (A "head" in Mercurial is a revision without children.) Can something similar be done in Git? I'd like to provide my co-workers with a command which they can always use to push their changes to a central repository in order that I can see what has happened and do merges accordingly. In Mercurial, such a command would simply be "hg commit && hg push -f". Then I can use "hg heads" to see if any new heads have grown, and if so, do merges. Upon their next pull, these merges would manifest themselves in the repositories of my co-workers, and everything will be fine for them. So, im looking for the equivalent of that workflow in Git. Thanks a lot!