[llvm] [Doc] Add a section on CI to the GitHub documentation (PR #85376)

[Mehdi Amini via llvm-commits]

https://github.com/joker-eph updated https://github.com/llvm/llvm-project/pull/85376

>From 78a1d6aa1185646ffd914785a46ce2db4396c254 Mon Sep 17 00:00:00 2001
From: Mehdi Amini <joker.eph at gmail.com>
Date: Fri, 15 Mar 2024 02:44:34 -0700
Subject: [PATCH] [Doc] Add a section on CI to the GitHub documentation

---
 llvm/docs/Contributing.rst | 22 +++++++++++++++++-----
 llvm/docs/GitHub.rst       | 22 ++++++++++++++++++++++
 2 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/llvm/docs/Contributing.rst b/llvm/docs/Contributing.rst
index dc8be93463cec1..34d9969f85ce20 100644
--- a/llvm/docs/Contributing.rst
+++ b/llvm/docs/Contributing.rst
@@ -124,12 +124,24 @@ For developers to commit changes from Git
 -----------------------------------------
 
 Once a patch is reviewed, you can select the "Squash and merge" button in the
-GitHub web interface. You might need to rebase your change before pushing
-it to the repo.
+GitHub web interface.
 
-LLVM currently has a linear-history policy, which means that merge commits are
-not allowed. The `llvm-project` repo on github is configured to reject pushes
-that include merges, so the `git rebase` step above is required.
+When pushing directly from the command-line to the ``main`` branch, you will need
+to rebase your change. LLVM has a linear-history policy, which means
+that merge commits are not allowed and the ``main`` branch is configured to reject
+pushes that include merges.
+
+GitHub will display a message that looks like this:
+
+.. code-block:: console
+
+  remote: Bypassed rule violations for refs/heads/main:
+  remote:
+  remote: - Required status check “buildkite/github-pull-requests” is expected.
+
+This can seem scary, but this is just an artifact of the GitHub setup: it is
+intended as a warning for people merging pull-requests with failing CI. We can't
+disable it for people pushing on the command-line.
 
 Please ask for help if you're having trouble with your particular git workflow.
 
diff --git a/llvm/docs/GitHub.rst b/llvm/docs/GitHub.rst
index 4010958c5d3133..a7c203e30ed407 100644
--- a/llvm/docs/GitHub.rst
+++ b/llvm/docs/GitHub.rst
@@ -176,6 +176,28 @@ request will understand that you're rebasing just your patches, and display
 this result correctly with a note that a force push did occur.
 
 
+Pre-merge Continuous Integration (CI)
+-------------------------------------
+
+Multiple checks will be applied on a pull-request, either for linting/formatting
+or some build and tests. None of these are perfect and you will encounter
+false positive, infrastructure failures (unstable or unavailable worker), or
+you will be unlucky and based your change on a broken revision of the main branch.
+
+None of the checks are strictly mandatory: these are tools to help us build a
+better codebase and be more productive (by avoiding issues found post-merge and
+possible reverts). As a developer you're empowered to exercise your judgement
+about bypassing any of the checks when merging code.
+
+The infrastructure can print messages that make it seem like these are mandatory,
+but this is just an artifact of GitHub infrastructure and not a policy of the
+project.
+
+However, please make sure you do not force-merge any changes that have clear
+test failures directly linked to your changes. Our policy is still to keep the
+``main`` branch in a good condition, and introducing failures to be fixed later
+violates that policy.
+
 Problems After Landing Your Change
 ==================================