Add new job failure reason
Problem to solve
When job fails during the git phase (clone/fetch) there is a high chance it's due to cache reason. Add a new banner on the job log page similar to system failure.
Target audience
Sasha is trying to set up sub modules just like in https://gitlab.com/gitlab-org/gitlab-ce/issues/55408 but notices the same issue. When the job fails she would see a red banner with a hint to clear the runner cache.
Further details
This came out from a discussion in https://gitlab.com/gitlab-org/gitlab-ce/issues/55408#note_129650537
Proposal
During the git clone/fetch phase on failure, GitLab Runner will return a new error, in which the frontend has to show a red banner specifying that it failed to pull the project and to suggest to clear the cache.
What does success look like, and how can we measure that?
People are less confused