CE port for pipelines for external pull requestsce-detect-github-pull-requests

Detect if pipeline runs for a GitHub pull request

When using a mirror for CI/CD only we register a pull_request
webhook. When a pull_request webhook is received, if the
source branch SHA matches the actual head of the branch in the
repository we create immediately a new pipeline for the
external pull request. Otherwise we store the
pull request info for when the push webhook is received.

When using "only/except: external_pull_requests" we can detect
if the pipeline has a open pull request on GitHub and create or
not the job based on that.

2 files changed, 12 insertions, 1 deletions

diff --git a/app/models/ci/pipeline.rb b/app/models/ci/pipeline.rb
index 2b6f10ef79f..e34c6204742 100644
--- a/app/models/ci/pipeline.rb
+++ b/app/models/ci/pipeline.rb
@@ -23,6 +23,7 @@ module Ci
     belongs_to :auto_canceled_by, class_name: 'Ci::Pipeline'
     belongs_to :pipeline_schedule, class_name: 'Ci::PipelineSchedule'
     belongs_to :merge_request, class_name: 'MergeRequest'
+    belongs_to :external_pull_request
 
     has_internal_id :iid, scope: :project, presence: false, init: ->(s) do
       s&.project&.all_pipelines&.maximum(:iid) || s&.project&.all_pipelines&.count
@@ -64,6 +65,11 @@ module Ci
     validates :merge_request, presence: { if: :merge_request_event? }
     validates :merge_request, absence: { unless: :merge_request_event? }
     validates :tag, inclusion: { in: [false], if: :merge_request_event? }
+
+    validates :external_pull_request, presence: { if: :external_pull_request_event? }
+    validates :external_pull_request, absence: { unless: :external_pull_request_event? }
+    validates :tag, inclusion: { in: [false], if: :external_pull_request_event? }
+
     validates :status, presence: { unless: :importing? }
     validate :valid_commit_sha, unless: :importing?
     validates :source, exclusion: { in: %w(unknown), unless: :importing? }, on: :create
@@ -675,6 +681,10 @@ module Ci
           variables.append(key: 'CI_MERGE_REQUEST_TARGET_BRANCH_SHA', value: target_sha.to_s)
           variables.concat(merge_request.predefined_variables)
         end
+
+        if external_pull_request_event? && external_pull_request
+          variables.concat(external_pull_request.predefined_variables)
+        end
       end
     end
 
diff --git a/app/models/ci/pipeline_enums.rb b/app/models/ci/pipeline_enums.rb
index 571c4271475..0c2bd0aa8eb 100644
--- a/app/models/ci/pipeline_enums.rb
+++ b/app/models/ci/pipeline_enums.rb
@@ -23,7 +23,8 @@ module Ci
         api: 5,
         external: 6,
         chat: 8,
-        merge_request_event: 10
+        merge_request_event: 10,
+        external_pull_request_event: 11
       }
     end