Refined-github: Update feature `linkify-branch-refs`

[fregante]

It's been added by GitHub, however their version doesn't add a strike-through to deleted branches. Perhaps the feature should just add a strike-through.

Testing threads:

• deleted branch: https://github.com/sindresorhus/refined-github/pull/576
• deleted branch (from fork): https://github.com/sindresorhus/refined-github/pull/872
• restored branch (on fork): https://github.com/sindresorhus/refined-github/pull/909

[sindresorhus]

Perhaps the feature should just add a strike-through.

👍

[fregante]

Ah, GitHub's own linkifier doesn't linkify the branch in the QuickPR page (https://github.com/sindresorhus/refined-github/issues/691), so maybe we should only limit the scope.

[jerone]

The feature linkify-branch-refs currently adds double links on PR:

[gurrrung]

@jerone So we have to remove unwanted one, right?

[fregante]

This issue is to be solved in 3 parts:

1. Avoid linkifying the branches on PRs: done in cb8de12e
2. Only add a strike through on deleted branches in PRs
3. Keep linkifying “quick PR” pages: done in cb8de12e

[fregante]

This is now mostly solved. I'm moving back to #2274 because it's more specific.