[TxMt] How does Git bundle choose what to commit?

[Dr. Drang]

Let's say I have a project folder open in TM. The folder has already
been initialized with Git, and all the files that are supposed to be
under source control have been added. Let's further say that I've made
some changes to the files "sample.html" and "sample.css," and it's
time for a commit. The sample.css file is the current tab and is the
file I've been editing most recently. I hit Control-Shift-G, the Git
command menu pops up, and I choose Commit. Up pops a browser/message
window with the words

    Committing Files in ‘sample.css’ on branch ‘master’

In front of that is a two-paned window. The top pane has a place for
me to type in the commit message, and the bottom shows a list of files
to commit. Even though I've changed both sample.html and sample.css,
only sample.css is in that list.

If I click in the project drawer before pressing Control-Shift-G,
things work the way I think they should: The browser/message window
says

    Committing Files in ‘./’ on branch ‘master’

and the two-paned window has both files in the list of files to commit.

Is there a way (apart from clicking in the project drawer) to get the
commit to apply to the entire project instead of just the frontmost
tab?

-- 
Dr. Drang