From 5f4720556ed797d04ffad709c8b2a98f34741211 Mon Sep 17 00:00:00 2001
From: Hartley McGuire <skipkayhil@gmail.com>
Date: Sat, 20 Sep 2025 15:05:48 -0400
Subject: [PATCH] Automatically ci-skip if all changed files are md

Currently, documentation changes require contributors to add a variation
of "ci skip" to their pull request in order to not run the full Rails
test suite. However, it requires contributors to know about this feature
in order to use it (to get faster/less flaky builds).

This commit tries to remove the requirements of that knowledge by
automatically skipping the full test suite in some cases (currently when
all changed files are markdown).

It also introduces a new opt-out "ci full" which can be used in cases
where the automatic opt-out is undesired for some reason.
---
 lib/buildkite/config/build_context.rb | 11 +++++++++++
 pipelines/rails-ci/pipeline.rb        |  2 +-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/lib/buildkite/config/build_context.rb b/lib/buildkite/config/build_context.rb
index c5f7760..da68a37 100644
--- a/lib/buildkite/config/build_context.rb
+++ b/lib/buildkite/config/build_context.rb
@@ -23,11 +23,22 @@ def nightly?
       ENV.has_key?("RAILS_CI_NIGHTLY")
     end
 
+    def full?
+      # [ci full], [full ci], [ci-full], or [full-ci]
+      [ENV["BUILDKITE_MESSAGE"], FetchPr.title].grep(/(ci full|full ci|ci-full|full-ci)/i).any?
+    end
+
     def skip?
       # [ci skip], [skip ci], [ci-skip], or [skip-ci]
       [ENV["BUILDKITE_MESSAGE"], FetchPr.title].grep(/(ci skip|skip ci|ci-skip|skip-ci)/i).any?
     end
 
+    def only_markdown?
+      `git diff --name-only $BUILDKITE_PULL_REQUEST_BASE_BRANCH`
+        .lines(chomp: true)
+        .all? { |line| line.end_with? ".md" }
+    end
+
     def rails_root
       Pathname.pwd
     end
diff --git a/pipelines/rails-ci/pipeline.rb b/pipelines/rails-ci/pipeline.rb
index fe59733..f8dc4a7 100644
--- a/pipelines/rails-ci/pipeline.rb
+++ b/pipelines/rails-ci/pipeline.rb
@@ -42,7 +42,7 @@
     end
   end
 
-  if build_context.skip?
+  if !build_context.full? && (build_context.skip? || build_context.only_markdown?)
     command do
       label ":bk-status-passed: Build skipped"
       skip true