Merge branch 'artifacts-from-ref-and-build-name' into 'master'

Add a download buttons for Build Artifacts

## What does this MR do?
This MR adds a download buttons for build artifacts of latest succesful pipeline in:
- dashboard of project,
- branches and tags views,
- and tree viewer

Implement #4255

## What are the relevant issue numbers?

Closes #4255, Closes #14419

## Screenshots

### Project main

![](/uploads/29ee2154a214416059a875f2715d4fa3/Screen_Shot_2016-08-24_at_8.00.31_PM.png)

### Branches

![](/uploads/9220c593288370986fbc1d42a1425ef7/Screen_Shot_2016-08-24_at_8.02.01_PM.png)

### Tags

![](/uploads/a843e8103221fea475a0cf9d62a1999d/Screen_Shot_2016-08-24_at_8.03.32_PM.png)

### Source Tree

![](/uploads/63cd3c8c91b6f427c166dc90d8e3c059/Screen_Shot_2016-08-24_at_8.04.56_PM.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] Download buttons
- [x] Models
- [x] Routes
- [x] Projects::ArtifactsController
- [x] API
- Tests
  - Rails
      - [x] Project#builds_for
      - [x] branch name with slashes
      - [x] only success builds
      - [x] only latest builds
      - [x] feature tests for download buttons
  - API
      - [x] branch name with slashes
      - [x] only success builds
      - [x] only latest builds
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5142

1 files changed, 9 insertions, 4 deletions

diff --git a/app/models/project.rb b/app/models/project.rb
index 0fa41ebbec3..c34064f96ce 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -436,7 +436,7 @@ class Project < ActiveRecord::Base
 
   # ref can't be HEAD, can only be branch/tag name or SHA
   def latest_successful_builds_for(ref = default_branch)
-    latest_pipeline = pipelines.latest_successful_for(ref).first
+    latest_pipeline = pipelines.latest_successful_for(ref)
 
     if latest_pipeline
       latest_pipeline.builds.latest.with_artifacts
@@ -1100,12 +1100,17 @@ class Project < ActiveRecord::Base
     !namespace.share_with_group_lock
   end
 
-  def pipeline(sha, ref)
+  def pipeline_for(ref, sha = nil)
+    sha ||= commit(ref).try(:sha)
+
+    return unless sha
+
     pipelines.order(id: :desc).find_by(sha: sha, ref: ref)
   end
 
-  def ensure_pipeline(sha, ref, current_user = nil)
-    pipeline(sha, ref) || pipelines.create(sha: sha, ref: ref, user: current_user)
+  def ensure_pipeline(ref, sha, current_user = nil)
+    pipeline_for(ref, sha) ||
+      pipelines.create(sha: sha, ref: ref, user: current_user)
   end
 
   def enable_ci