If I'm understanding you correctly, this is wrong. You can add individual lines in a file to your commit. That's one of the main uses I have for the app: it's easier to split up file changes between commits than on the command line. See this screenshot: http://imgur.com/a/4CQG7 You have to click on the line numbers to add/remove individual lines.
- First I thought you select lines, like other git apps. No, it's not just that numbered line, it's the actual digits on the left.
- Then I selected some digits, expecting a 'stage' button to appear.
Then finally I realised just selecting the lines committed only them.
Even working out how to do it, it's still weird because lines with blue digits now get committed, lines with green ones don't.
You could submit an issue or a pull request with suggestions on what a more obvious UI might be!