Add improvements to merge request versions

* show commits count in the merge request version dropdown
* initialize base/start commit sha for old merge request diffs from repo
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/models/merge_request_diff.rb

@@ -34,7 +34,9 @@ class MergeRequestDiff < ActiveRecord::Base
     if persisted?
       # Workaround for old MergeRequestDiff object
       # that does not have head_commit_sha in the database
-      self.head_commit_sha ||= last_commit.sha
+      self.start_commit_sha ||= merge_request.target_branch_sha
+      self.head_commit_sha  ||= last_commit.sha
+      self.base_commit_sha  ||= find_base_sha
     else
       self.start_commit_sha ||= merge_request.target_branch_sha
       self.head_commit_sha  ||= merge_request.source_branch_sha

app/views/projects/merge_requests/show/_versions.html.haml

@@ -20,8 +20,9 @@
                 #{merge_request_diff.head_commit.short_id}
               %br
               %small
+                #{number_with_delimiter(merge_request_diff.commits.count)} #{'commit'.pluralize(merge_request_diff.commits.count)},
                 = time_ago_with_tooltip(merge_request_diff.created_at)
 
     .pull-right
       %span.monospace
-        git diff #{@merge_request_diff.base_commit.short_id}..#{@merge_request_diff.head_commit.short_id}
+        #{@merge_request_diff.base_commit.short_id}..#{@merge_request_diff.head_commit.short_id}