Fix web display of merge trains

[rudymatela]

Closes: #162
Closes: #163

This PR fixes the web display of merge trains:

• display PRs in the order they were approved which is the order of the train
  (closes Order PRs in the web interface by approval #162);
• display speculative rebase failures
  (closes Display speculative rebase failures properly on the web interface #163);
• refactor WebInterface to remove repeated code with the classifiedPullRequests function;
• different icons and text for all possible integration statuses: 🟡❌✅ 🔷❗;
• add some automated tests to classifiedPullRequests;
• take screenshots and place them here;

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Before merge actions (unchanged)

⬆️ Nothing changes when all PRs are waiting for review.

These PRs were approved in the following order:

• (Re-)infer candidate from state #141
• Test the build status comment. #143
• Hoff does not re-run tests unless there has been any other PRs merged #142
• Hoff sometimes posts duplicate comments #144
• Test comments looping back from GitHub (on top of v0.25.7) #140

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Before (repository view)

⬆️ note PR #142 (Squidward) is missing and PRs are not listed in order of approval.

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After (repository view)

⬆️ correct order, no duplicates, icons

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Before (global view)

⬆️ note PR #142 (Squidward) is missing and PRs are not listed in order of approval. There is one PR that is duplicate!

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After (global view)

⬆️ correct order, no duplicates, icons

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[rudymatela]

There were changes on master. Better rebase now than later...

[rudymatela]

This is ready for review.

@frank-channable or @alex-mckenna can either of you please review? (whoever is free first -- first-come-first-merged)

[alex-mckenna]

I have no real comments about the code, it all looks pretty clean to me. I do wonder if now that more is displayed it's losing some clarity.

The emoji indicators are cute, but as we have more they become less obvious. The blue diamond for promoted feels odd, but I can't think of a good choice for this. Text only also has problems though, because it becomes a bit more difficult to just scan the page with your eyes... What do you think?

[rudymatela]

The emoji indicators are cute, but as we have more they become less obvious. The blue diamond for promoted feels odd, but I can't think of a good choice for this. Text only also has problems though, because it becomes a bit more difficult to just scan the page with your eyes... What do you think?

It does feel hard to parse in the case I presented. However in practice we expect to seldom encounter icons other than 🟡 and ❌:

• ✔️ - this will only appear if the build of the second/third/etc PRs in the train terminates before the build of the first. This does happen in practice if builds are started almost at the same time, but usually the first PR would be about to finish building. So this should only be in place for brief window;
• ❗ ❗ Since the start of the month, rebase failures have only happened 17 times. That's 0.68 times per day taking into account all 26 projects we track. If we open the global view and scroll to the page, we expect to see one for a few hours once every couple of days.
• ❗ merge rejections due to wrong target branch have happened only once this month!
• 🔷 As soon as a PR is promoted, it is deleted from the Hoff state. So I don't expect this to appear in the UI actually. I've put the option there in case we end up displaying it (by accident or by future decision). I've added a comment noting this.

The interface state shown here is a bit of an extreme example illustrating all states:

In practice we normally see something like:

• Building
  • ... 🟡
  • ... 🟡
  • ... 🟡
• Failed
  • ... ❌
  • ... ❌
  • ... ❌
  • ... ❌

Other icons will be more like exceptions:

• Building
  • ... 🟡
  • ... 🟡
  • ... 🟡
• Failed
  • ... ❌
  • ... ❌
  • ... ❗ incorrect base branch
  • ... ❌

... or only shown during a brief window:

• Building
  • ... 🟡
  • ... ✔️
  • ... 🟡
• Failed
  • ... ❌
  • ... ❌
  • ... ❌
  • ... ❌

PS: here are the two queries:

journalctl -u hoff -S2022-08-01 | grep "Posted.*Failed to rebase"
journalctl -u hoff -S2022-08-01 | grep "Posted.*Merge rejected:"

[alex-mckenna]

Hmm, okay. That seems reasonable then. Thanks for adding the comment 👍

PS: Good to know, you don't need sudo for those commands by the way

[rudymatela]

@alex-mckenna Thanks for the review. 🎉

@OpsBotPrime merge 🚢 🚀

[OpsBotPrime]

Pull request approved for merge by @rudymatela, rebasing now.

[OpsBotPrime]

Rebased as 00dd4ad, waiting for CI …

[OpsBotPrime]

CI job 🟡 started.