how can I stage a single line in SmartGit?

I want to stage a single line in SmartGit, rather than a whole diff hunk.

Eg:

old line
new line but leave unstaged
new line, just stage this
new line but leave unstaged
new line but leave unstaged
old line

This is doable with GitX on OS X but on SmartGit the smallest unit I appear to be able to stage is a whole set of diff lines.

What is Smartgit stage?

To stage a file is simply to prepare it finely for a commit. Git, with its index allows you to commit only certain parts of the changes you've done since the last commit. Say you're working on two features – one is finished, and one still needs some work done.

Use Local|Index Editor: you can edit the Index file content as you like there.