Rename latest_pipeline to last_pipeline

As it might be confusing that it's not the same as
Pipeline#latest

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11038#note_28677090

app/models/commit.rb

@@ -236,8 +236,8 @@ class Commit
     project.pipelines.where(sha: sha)
   end
 
-  def latest_pipeline
-    @latest_pipeline ||= pipelines.last
+  def last_pipeline
+    @last_pipeline ||= pipelines.last
   end
 
   def status(ref = nil)

app/views/projects/commit/_commit_box.html.haml

@@ -61,20 +61,20 @@
     %span.commit-info.branches
       %i.fa.fa-spinner.fa-spin
 
-  - if @commit.latest_pipeline
-    - latest_pipeline = @commit.latest_pipeline
+  - if @commit.last_pipeline
+    - last_pipeline = @commit.last_pipeline
     .well-segment.pipeline-info
       .status-icon-container{ class: "ci-status-icon-#{@commit.status}" }
-        = link_to namespace_project_pipeline_path(@project.namespace, @project, latest_pipeline.id) do
-          = ci_icon_for_status(latest_pipeline.status)
+        = link_to namespace_project_pipeline_path(@project.namespace, @project, last_pipeline.id) do
+          = ci_icon_for_status(last_pipeline.status)
       Pipeline
-      = link_to "##{latest_pipeline.id}", namespace_project_pipeline_path(@project.namespace, @project, latest_pipeline.id), class: "monospace"
-      = ci_label_for_status(latest_pipeline.status)
-      - if latest_pipeline.stages.any?
+      = link_to "##{last_pipeline.id}", namespace_project_pipeline_path(@project.namespace, @project, last_pipeline.id), class: "monospace"
+      = ci_label_for_status(last_pipeline.status)
+      - if last_pipeline.stages.any?
         .mr-widget-pipeline-graph
-          = render 'shared/mini_pipeline_graph', pipeline: latest_pipeline, klass: 'js-commit-pipeline-graph'
+          = render 'shared/mini_pipeline_graph', pipeline: last_pipeline, klass: 'js-commit-pipeline-graph'
       in
-      = time_interval_in_words latest_pipeline.duration
+      = time_interval_in_words last_pipeline.duration
 
 :javascript
   $(".commit-info.branches").load("#{branches_namespace_project_commit_path(@project.namespace, @project, @commit.id)}");

spec/models/commit_spec.rb

@@ -212,7 +212,7 @@ eos
     end
   end
 
-  describe '#latest_pipeline' do
+  describe '#last_pipeline' do
     let!(:first_pipeline) do
       create(:ci_empty_pipeline,
         project: project,
@@ -226,8 +226,8 @@ eos
         status: 'success')
     end
 
-    it 'returns latest pipeline' do
-      expect(commit.latest_pipeline).to eq second_pipeline
+    it 'returns last pipeline' do
+      expect(commit.last_pipeline).to eq second_pipeline
     end
   end