Add cancel button next to commit (amend, empty-commit)

[ylecuyer]

Add a cancel button next to the commit button in the staging view.
Currently, when you're amending a commit or committing an empty commit you have to refresh to cancel.

[jung-kim]

I don't understand the concept of canceling commit. A commit should be final, and if you want to go back you can go back to the commit before and rework.

[campersau]

If there is nothing to commit you see this:

In #1030 a second link will appear and it is not possible to go back to this view after you clicked on one of the links without refreshing the page.

[jung-kim]

Am I understanding correctly that we are adding #1028 and that implementation, #1030, now needs cancel button?