Add possibility define on_failure and on_success after_script

UPDATE

With the introduction of CI_JOB_STATUS you can add to the after_script and if statement which checks the CI_JOB_STATUS

Hello.

Description

I especially want such thing for per-job basis. Main purpose do different things depemdent from job status. Like tag built docker image on success with latest, or clean also intermediate images, run containrs etc…

Proposal

Example:

before_script:
- global before script

job:
  before_script:
  - execute this instead of global before script
  script:
  - my command
  after_script:
   when: on_failure
   - execute this after my script if it failed
  after_script:
   when: on_success
   - execute this after my script if it success

Links / references

https://docs.gitlab.com/ce/ci/yaml/README.html#before_script-and-after_script