Link to CI build artefacts doesn't work when source and target branch is the same

[michalkleiner]

It's not very common but can happen when community members don't use a new branch and open a PR from their fork within the same branch name.

Example PR — matomo-org/matomo#20969

Target branch: 5.x-dev
Source branch: 5.x-dev

The link to the assets from UI tests is missing the branch as it probably evaluated there's no branch, and therefore the link doesn't present anything (goes to 404).

Stretch goal: When looking into this, we could also address branches with slashes in them to work as expected, which might be a configuration within the builds webserver. Alternatively we can replace slashes with some filesystem-indifferent character.

[sgiehl]

@michalkleiner I actually don't think the branch name is the problem here.
The artifacts can only be uploaded if the password is provided, but the password is stored in a github secret. Pull requests from foreign repos don't have access to the secrets, so the upload fails. See https://github.com/matomo-org/matomo/actions/runs/5468933422/jobs/9957228165?pr=20969#step:3:2827

[michalkleiner]

Ah, ok. Well, in that case we can probably close this as there's not much we can do as that could be a DDoS attack vector if we allowed external PRs to fill up the builds storage space.