dlvr.it allows you to create filters on items. You can get it to post as much or as little as you want and it provides full customization for formatting, you can even find and replace within the text
It's pretty hard to get formatting you need with rss feed.
In some cases formatting human readable tweet require addition GET query to github API and many other more specific problems.
dlvr.it is just to general to be good for one thing.
tweethub is good for one thing.
Yeah it's one thing that does a very simple job that I have to give both my twitter and github auth too. I might forget about them or not be sure how to disable it. Are you going to build one of these for the 20 or so other feeds I put into my Twitter? Yeah it's a nice idea, and the implementation seems good, but it's not really fixing a problem so for most people it probably won't be worth the effort.
Let's assume you don't want to remember anything.
But once when you do a commit you might do it like:
git commit -m "Add magic beans to make super scale //tweet"
Is it easy enough?
Most services are useless for most people. It's true. I built it because I need it myself. But I can assume there some people just like me in the world.
dlvr.it provides this out of the box. There are probably other services that do the same. I think TwitterFeed provides options for only posting certain content but it's been a while since I used it
I tried twitterfeed on my own and All reasons above makes this approach not really good.