As a follow-up to this question:

If I'm working on a team by myself, I can maintain useful commit messages when merging branches by squashing all the commits to a single diff and then merging that diff. That way I can easily see what changes were introduced in the branch, and I have a single summary describing the feature/change/whatever that was accomplished in that branch when browsing the master branch.

My question now is, how can I accomplish this when working with a team? In that situation, the branches will be pushed to a remote repository, meaning that I can't squash all the commits in the branch down to a single commit. If the branch is public, can I still have a single useful merge commit in the master branch? (By "useful" I mean that the commit in the master line tells me (1) a useful summary of what was done in the branch and (2) diffs of the same.)