Why does the beginning of `git log` for the Bitcoin source on github say 'sirius-m' was the first committer? Satoshi Nakamoto is widely spoken of as being the first committer to bitcoin.

Yesterday I ran gource on the bitcoin repo for fun and was surprised to see that the first commits were by 'sirius-m', or Martti Malmi.

Was there a previous repo in another svn tool and did Martti just do the first commit in git?

It really looks like Martti is the initial committer if you look at the git repo on Github...
The source code was originally hosted in a rar file on Bitcoin.org. It did not use any Source Control Management. Later, when more people began working on it, one of the earliest developers, Sirius, moved everything to SVN on Sourceforge. That was later moved to the current Github repository and switched to using Git.