pipelines branches - not master

[Samantha Adrichem]

Is it possible to use a regexp on this syntax

branches:
    feature/*:

To declare it as not master with a regexp of some sort? For example

^(?!master$).*

For example we have a job for unittests, and want it run on all branches except master.

There is no job for the master branch.

if not, is this possible?

branches:
    development:
    branch-*:
      - step