Fetch locals to avoid undefined method/local error

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7034/diffs#note_17868074

app/views/projects/_last_commit.html.haml

+- ref = local_assigns.fetch(:ref)
 - status = commit.status(ref)
 - if status
   = link_to builds_namespace_project_commit_path(commit.project.namespace, commit.project, commit), class: "ci-status ci-#{status}" do

app/views/projects/commits/_commit.html.haml

+- ref = local_assigns.fetch(:ref)
 - if @note_counts
   - note_count = @note_counts.fetch(commit.id, 0)
 - else

app/views/projects/commits/_commits.html.haml

+- ref = local_assigns.fetch(:ref)
 - commits, hidden = limited_commits(@commits)
 
 - commits.chunk { |c| c.committed_date.in_time_zone.to_date }.each do |day, commits|