Using bash substitution parameter in gitlab-ci.yml

Hello,

I would like to make some substitution in pre-defined environment variables before running a job (using Bash’s Shell Parameter Expansion feature)

Example:

build_pkg:
  image: myuser/myimage:${CI_COMMIT_TAG%.*}
  script:
   - make

I was not able to make it working and didn’t find anything in docs related to that feature.

If this feature doesn’t exist yet, I will find helpul to have it.