First of all, get the git bundle.
ted$ cd ~/Library/Application\ Support/TextMate/Bundles
ted$ git clone git://gitorious.org/git-tmbundle/mainline.git
empty Git repository in /Users/ted/Library/Application
Counting objects: 5018, done.
Compressing objects: 100% (1612/1612), done.
Total 5018 (delta 3342), reused 4957 (delta 3303)
objects: 100% (5018/5018), 634.79 KiB | 181 KiB/s, done.
deltas: 100% (3342/3342), done.
Then, invoke Textmate and navigate to Bundles->Git->Administration
->Update Git Bundle. The following screen appears.
Here are some references.
This Textmate git bundle seems to work pretty well. Here's how I
tried it out. First of all use Textmate to open a file that is a
member of a git repository. Make a change and save it. Then, from the
Textmate window do a Bundles -> Git -> Commit.
Double click on the filename in the Choose files to commit pane. A
Textmate window opens up that shows the file in a diff format.
Write a description in the Summary of changes pane. Click commit.
The window with the Summary and Commit button disappears and the
other window shows what happened.
I still have the two Textmate windows open. Close the one with the
diff and select the one with the file. Then, from the Textmate menu
do a Bundles -> Git -> Log, and the following window appears.