Git store whole files. The diff and the merge algorithm works by line by default, but that's because line is a rough unit of code (statement, expression, and definition happens mostly within one line).
I absolutely love the images on the landing page. "Inappropriate use of blame, push and pull to resolve a conflict" is pure genius. Even the name had a lot of thought put into it (didn't know about "Giraffe language" before). Beautiful! :)
As someone who learned a lot from Non-Violent Communication, discovering mergiraf went something like
> ...oh, cool - I've wanted this for years, great that someone buckled down and wrote it.
>
> Why 'mergiraf,' though?
>
> [Sees NVC link on the site]
>
> ...OH. Conflict resolution through understanding. That's absolutely brilliant, at so many levels.