Alternative approach for comments-time-machine-links

[fregante]

The timemachine link is useful but I never click it unless I really need that version, and most of the time I don't know this until I click the main link.

I suggest dropping the icon (closes #2131) and, instead, waiting for the user to click the link.

On the resulting page:

• if the linked file still exists, add the timemachine permalink near branch-buttons:
  
• if the linked file is gone, add the timemachine link somewhere on the 404 page

This also makes it easier to enable #1953 because we don't have to query each link on the page before adding the link: we just query the current page.

---

For this to be possible, instead of adding an icon to these links, we should add a ?linked-time=${timestamp} parameter so this information is available on the linked page.

Test

• Still exist: https://github.com/sindresorhus/refined-github/blob/master/source/features/comments-time-machine-links.tsx#L6-L8
• File deleted: https://github.com/sindresorhus/refined-github/blob/master/source/features/default-to-rich-diff.tsx#L19

[sindresorhus]

Sounds good 👍

[fregante]

Here's something easy to add in both cases (existing file or 404 page) and easy to understand:

Example code:

<div id="js-flash-container">
  <div class="flash flash-full flash-notice">
	  <div class="container-lg px-2">
	    <button class="flash-close js-flash-close" type="button" aria-label="Dismiss this message">{xIcon()}</button>
		You can also <a href="">view this file as it appeared at the time of the comment</a> (4 days ago)
		</div>
	</div>
</div>