You can access a “Smart Folder” from the top bar of the folder drawer by clicking on the purple folder with a gear on it. This folder gives you a view of ‘Uncommitted Changes’ and ‘Untracked Files’ in your project*.
You can select files you want to commit using the Git bundle’s “Commit…” command (makes it easier if assign a shortcut to this menu item — maybe ⌘⌥⌃C — though you can use this tip to find one that doesn’t conflict).
You can also access a diff viewer from here which opens within textmate itself. Not ideal compared to GitX or Github, but for small commits it’s nice to not have to switch away from Textmate.
*This requires that you are using a source control system such as Git, Subversion or Mercurial, and that you have configure the proper path in .tm_properties.
Git status in file browser
If you’ve configured your .tm_properties file to point to your installation of git, the file browser will display source control status icons on your files.
You can see this on the index.php and header.php files in the repo above, both of which have not-yet-committed changes, and are displaying small blue circle icons.