Create framework for build prerequisites

Introduces the concept of Prerequisites for a CI build.
If a build has unmet prerequisites it will go through the
:preparing state before being made available to a runner.

There are no actual prerequisites yet, so current
behaviour is unchanged.

1 files changed, 8 insertions, 1 deletions

diff --git a/app/models/commit_status.rb b/app/models/commit_status.rb
index bfb13fa0ce8..5f66a661324 100644
--- a/app/models/commit_status.rb
+++ b/app/models/commit_status.rb
@@ -66,7 +66,10 @@ class CommitStatus < ActiveRecord::Base
     end
 
     event :enqueue do
-      transition [:created, :preparing, :skipped, :manual, :scheduled] => :pending
+      # A CommitStatus will never have prerequisites, but this event
+      # is shared by Ci::Build, which cannot progress unless prerequisites
+      # are satisfied.
+      transition [:created, :preparing, :skipped, :manual, :scheduled] => :pending, unless: :any_unmet_prerequisites?
     end
 
     event :run do
@@ -180,6 +183,10 @@ class CommitStatus < ActiveRecord::Base
     false
   end
 
+  def any_unmet_prerequisites?
+    false
+  end
+
   def auto_canceled?
     canceled? && auto_canceled_by_id?
   end