Check external links once a month

[koppor]

Test external links in documentation

Context and Problem Statement

The JabRef repository contains Markdown (.md) files documenting the JabRef code.
The documentation contains links to external resources.
For high-quality documentation, external links should be working.

Currently we check at each PR (option 2 below), but that is annoying. See #6677.

Decision Drivers

• Checking external links should not cause issues in the normal workflow

Considered Options

• Check external links once a month
• Check external links in the "checkstyle" task
• Do not check external links

Decision Outcome

Chosen option: "[option 1]", because [justification. e.g., only option, which meets k.o. criterion decision driver | which resolves force force | … | comes out best (see below)].

Positive Consequences

• Automatic notification of broken external links

Negative Consequences

• Some external sites need to be disabled. For isntance, GitHub.com always returns "forbidden". A filter for status is future work of the used tool.

Pros and Cons of the Options

Check external links once a month

• Good, because does not interfer with the normal development workflow
• Bad, because an additional workflow is required

Check external links in the "checkstyle" task

• Good, because no seperate workflow is required
• Bad, because checks fail independent of the PR (because external web sites can go down and go up independent of a PR)

Do not check external links

• Good, because no testing at all is required
• Bad, because external links break without any notice
• Bad, because external links have to be checked manually

• Change in CHANGELOG.md described (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked documentation: Is the information available and up to date? If not created an issue at https://github.com/JabRef/user-documentation/issues or, even better, submitted a pull request to the documentation repository.

[tobiasdiez]

Thanks!