Proposal: Feature to check that a PR description includes closure keywords

[rgee0]

Expected Behaviour

Addition of a new feature to check the contents of a PR description for a referenced issue number. See: https://help.github.com/articles/closing-issues-using-keywords/ for a full explanation.

Current Behaviour

A PR is raised with an issue reference but without a closure keyword. This results in manual activity to keep repo issues in sync with project state.

Possible Solution

Similar to the sign-off check. Test the incoming detail for GitHub closure keywords:

close
closes
closed
fix
fixes
fixed
resolve
resolves
resolved

alongside an issue reference. Further detail on the format of these is available at the aforementioned link.

On receipt of a PR without a closure Derek should apply a label, such as no-issue, unlinked, no-closure and post a comment to provide the user with the information required to help them update the description.

Steps to Reproduce (for bugs)

Not a bug

Context

Enabling the ability for Derek to apply more of a project's contributing guide through contributor education & prompting.

Your Environment

N/A

[alexellis]

I like the idea.