Git also comes with a SVN bridge, which works wonderfully for me.
Also ... Rails has its own development web-server. You don't need to have a production environment to learn it.
And I really recommend that when learning about any web framework, in any language ... just learn how to deploy a production server by yourself. It saves a lot of pain later on ;)
Not to mention that I wouldn't use Heroku ... sure they provide a valuable service, but personally I get a cheaper deal by getting EC2 instances and configuring them myself. It's hard the first time, but then you can scale your infrastructure easily ... EC2 is wonderful in that regard.
Sinatra doesn't have all that. A combination of Heroku, Sinatra, and DataMapper (nice, cleaner, simpler alternative to active record) and what you have is a very easy to deploy application.
I'm doing the above, and doing it on Windows (sorry, I'd love to use Linux but my wife uses this machine when I'm not and has some apps that are not replaceable, and I don't want to mess around with dual booting. So when I get FU money I'll be Linux all the way).
If you have any questions I'd be glad to help.