How to change merge message ("weenie commits")

I have developed a habit of using my SCM to provide local backup of my daily (hourly) work. I often will work to a stopping point and commit my work, without any real coherence to the commit --- a sort of checkpoint. These I call "weenie commits" because they are weenie-ish, unimportant in the larger scheme of things.

When developing with others, I would like to be able to work in this way, tidily keeping my stuff tucked away in my SCM system, and then when I am ready to share, to convey to my peers what they need to know about my work, and not the 10,000 weenie commit messages that may be associated with my work.

So, when I merge my topic branch onto master, for example, I'd like the commit message to be something more thoughtful than the "checkpoint 1", "checkpoint 2", "fix typo", "redo sort algorithm", etc., etc., and be more like a short set of release notes, a summary of what all has been accomplished.

Do others run into this and perhaps have a good solution?

Bill