Do you know GitX? It's perfect for quick git commits with line-by-line staging and unstaging.
[0] Up to date fork: https://rowanj.github.io/gitx/ [1] Original: http://gitx.frim.nl/
[0] Up to date fork: https://rowanj.github.io/gitx/ [1] Original: http://gitx.frim.nl/
(personal nitpick: I'd love if the app showed me how to use it rather than having to consult to online instructions)