gitlab gitlab-ci

How can I get the commit diff in Gitlab CI?

I use Gitlab CI for checking a code quality of my project. Sometime I want to check only new code ( new commit ).
How can I get diff from Gitlab CI ?

Solution

I found out solution, it was obvious, but not for me

 diff:
   script:
     - git diff ${CI_COMMIT_SHA} master
   except:
     - master