Staging Individual Lines

Hi,

I had a big commit I wanted to break up and was wondering if there is any way to stage individual lines from the command line.

I am using git add -i but it couldn't split the hunks any smaller.

I went looking on Google and found git-cola gui client which works for staging individual lines to the commit.

But it's a bit clumsy to do this with the mouse and I was wondering if there is a way to do this without having manually editing the file and changing the diff numbers in git add -i when it can't break the hunks smaller.

Why must we still manually edit the diff numbers when git-cola seems to be able to work out the changes automatically when adding single lines?

Thanks for your help.