Merge pull request #16 from input-output-hk/newhoggy/update-required-…

…checks

Add explanation and 'Incidents' section to cardano-node-required-checks page

docs/Cardano-node-required-checks.md

@@ -2,13 +2,25 @@
 
 These are the agreed-upon required checks for the [`cardano-node` repository](https://github.com/input-output-hk/cardano-node).
 
-Legend:
+Whenever there is a variation to this document, the required checks for the `cardano-node`
+repository should be updated accordingly.
+
+If the required checks for the `cardano-node` repository differ from those
+described here, then those should be updated to match this page.
+
+Sometimes, due to an urgent situation, a required check may need to be disabled
+to merge an important PR. Those incidents should be documented in the incidents
+section of the page. Keeping a list of such incidents will help us understand
+which required checks are problematic.
+
+### Legend
 * ✅ Required check.
   Merges disallowed unless this job is successful.
 * 👉 Pre-requisite required check.
   A required check depends on this job.  A job with a required check could not pass without this passing.
 * ⛔ No required check and not a pre-requisite.
 
+### Required Checks
 * ⛔ Check Markdown links / markdown-link-check (push)
 * ⛔ Check HLint / build (push)
 * ⛔ Check Stylish Haskell / build (push)
@@ -45,3 +57,7 @@ Legend:
 * ⛔ ci/eval
 * ✅ ci/hydra-build:required
 * ⛔ ci/pr/required
+
+### Incidents
+
+List emergency incidents here.