Fix blame view line groupings

Closes #2305

app/controllers/projects/blame_controller.rb

@@ -8,6 +8,28 @@ class Projects::BlameController < Projects::ApplicationController
 
   def show
     @blob = @repository.blob_at(@commit.id, @path)
-    @blame = Gitlab::Git::Blame.new(@repository, @commit.id, @path)
+    @blame = group_blame_lines
+  end
+
+  def group_blame_lines
+    blame = Gitlab::Git::Blame.new(@repository, @commit.id, @path)
+
+    prev_sha = nil
+    groups = []
+    current_group = nil
+
+    blame.each do |commit, line|
+      if prev_sha && prev_sha == commit.sha
+        current_group[:lines] << line
+      else
+        groups << current_group if current_group.present?
+        current_group = { commit: commit, lines: [line] }
+      end
+
+      prev_sha = commit.sha
+    end
+
+    groups << current_group if current_group.present?
+    groups
   end
 end

app/views/projects/blame/show.html.haml

@@ -13,30 +13,32 @@
     .file-content.blame.highlight
       %table
         - current_line = 1
-        - @blame.each do |raw_commit, line|
+        - @blame.each do |blame_group|
           %tr
             %td.blame-commit
               .commit
-                - unless @prev_commit && @prev_commit.sha == raw_commit.sha
-                  - commit = Commit.new(raw_commit, @project)
-                  .commit-row-title
-                    %strong
-                      = link_to_gfm truncate(commit.title, length: 35), namespace_project_commit_path(@project.namespace, @project, commit.id), class: "cdark"
-                    .pull-right
-                      = link_to commit.short_id, namespace_project_commit_path(@project.namespace, @project, commit), class: "monospace"
-                     
-                  .light
-                    = commit_author_link(commit, avatar: false)
-                    authored
-                    #{time_ago_with_tooltip(commit.committed_date)}
-                - @prev_commit = raw_commit
+                - commit = Commit.new(blame_group[:commit], @project)
+                .commit-row-title
+                  %strong
+                    = link_to_gfm truncate(commit.title, length: 35), namespace_project_commit_path(@project.namespace, @project, commit.id), class: "cdark"
+                  .pull-right
+                    = link_to commit.short_id, namespace_project_commit_path(@project.namespace, @project, commit), class: "monospace"
+                   
+                .light
+                  = commit_author_link(commit, avatar: false)
+                  authored
+                  #{time_ago_with_tooltip(commit.committed_date)}
             %td.lines.blame-numbers
               %pre
-                = current_line
-                - current_line += 1
+                - line_count = blame_group[:lines].count
+                - (current_line...(current_line + line_count)).each do |i|
+                  = i
+                  \
+                - current_line += line_count
             %td.lines
               %pre{class: 'code highlight white'}
                 %code
-                  :erb
-                    <%= highlight(@blob.name, line, nowrap: true, continue: true).html_safe %>
+                  - blame_group[:lines].each do |line|
+                    :erb
+                      <%= highlight(@blob.name, line, nowrap: true, continue: true).html_safe %>