Merge branch 'ci-commit-as-pipeline' into 'master'

Ci::Commit becomes a Pipeline object

1. Ci::Commit receives context: ref, :tag.
1. One Ci::Commit describes a one Pipeline
1. Pipeline is created from `.gitlab-ci.yml`
1. Pipeline is a ordered group of builds
1. We test MR against Pipeline
1. Pipelines have a separate view (https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3703)
1. Pipeline can be triggered from UI (https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3703)
1. Later we change `Trigger -> TriggerRequest -> Build` to `Trigger -> Pipeline` (future)
1. We add a Pipeline Hook that will be triggered on Pipeline status change  (future)
1. We extend notifications to use `Pipeline Hook` to send summary on pipeline changes (future)

After merging that I'll prepare a separate MR that will unify naming, database columns, table names:
```
Ci::Commit -> Pipeline
Ci::Build -> Build
CommitStatus -> Job
GenericCommitStatus -> ExternalJob

ci_commits -> pipelines
ci_builds -> jobs
```

This MR implements first 5 points.

This is made to solve this issue https://gitlab.com/gitlab-org/gitlab-ce/issues/14149.

See merge request !3653

1 files changed, 4 insertions, 3 deletions

diff --git a/app/models/commit.rb b/app/models/commit.rb
index 6bb018b086f..562c3ed15b2 100644
--- a/app/models/commit.rb
+++ b/app/models/commit.rb
@@ -207,12 +207,13 @@ class Commit
     @raw.short_id(7)
   end
 
-  def ci_commit
-    project.ci_commit(sha)
+  def ci_commits
+    @ci_commits ||= project.ci_commits.where(sha: sha)
   end
 
   def status
-    ci_commit.try(:status) || :not_found
+    return @status if defined?(@status)
+    @status ||= ci_commits.status
   end
 
   def revert_branch_name