1 files changed, 38 insertions, 5 deletions

diff --git a/app/models/merge_request_diff.rb b/app/models/merge_request_diff.rb
index 445179a4487..dd65a9a8b86 100644
--- a/app/models/merge_request_diff.rb
+++ b/app/models/merge_request_diff.rb
@@ -6,6 +6,9 @@ class MergeRequestDiff < ActiveRecord::Base
   # Prevent store of diff if commits amount more then 500
   COMMITS_SAFE_SIZE = 100
 
+  # Valid types of serialized diffs allowed by Gitlab::Git::Diff
+  VALID_CLASSES = [Hash, Rugged::Patch, Rugged::Diff::Delta]
+
   belongs_to :merge_request
 
   state_machine :state, initial: :empty do
@@ -30,6 +33,10 @@ class MergeRequestDiff < ActiveRecord::Base
     select(column_names - ['st_diffs'])
   end
 
+  def st_commits
+    super || []
+  end
+
   # Collect information about commits and diff from repository
   # and save it to the database as serialized data
   def save_git_content
@@ -83,7 +90,7 @@ class MergeRequestDiff < ActiveRecord::Base
   end
 
   def commits
-    @commits ||= load_commits(st_commits || [])
+    @commits ||= load_commits(st_commits)
   end
 
   def reload_commits
@@ -117,6 +124,14 @@ class MergeRequestDiff < ActiveRecord::Base
     project.commit(head_commit_sha)
   end
 
+  def commits_sha
+    if @commits
+      commits.map(&:sha)
+    else
+      st_commits.map { |commit| commit[:id] }
+    end
+  end
+
   def diff_refs
     return unless start_commit_sha || base_commit_sha
 
@@ -152,8 +167,24 @@ class MergeRequestDiff < ActiveRecord::Base
     self == merge_request.merge_request_diff
   end
 
+  def compare_with(sha, straight: true)
+    # When compare merge request versions we want diff A..B instead of A...B
+    # so we handle cases when user does squash and rebase of the commits between versions.
+    # For this reason we set straight to true by default.
+    CompareService.new.execute(project, head_commit_sha, project, sha, straight: straight)
+  end
+
   private
 
+  # Old GitLab implementations may have generated diffs as ["--broken-diff"].
+  # Avoid an error 500 by ignoring bad elements. See:
+  # https://gitlab.com/gitlab-org/gitlab-ce/issues/20776
+  def valid_raw_diff?(raw)
+    return false unless raw.respond_to?(:each)
+
+    raw.any? { |element| VALID_CLASSES.include?(element.class) }
+  end
+
   def dump_commits(commits)
     commits.map(&:to_hash)
   end
@@ -184,7 +215,7 @@ class MergeRequestDiff < ActiveRecord::Base
   end
 
   def load_diffs(raw, options)
-    if raw.respond_to?(:each)
+    if valid_raw_diff?(raw)
       if paths = options[:paths]
         raw = raw.select do |diff|
           paths.include?(diff[:old_path]) || paths.include?(diff[:new_path])
@@ -268,8 +299,10 @@ class MergeRequestDiff < ActiveRecord::Base
   end
 
   def keep_around_commits
-    repository.keep_around(start_commit_sha)
-    repository.keep_around(head_commit_sha)
-    repository.keep_around(base_commit_sha)
+    [repository, merge_request.source_project.repository].each do |repo|
+      repo.keep_around(start_commit_sha)
+      repo.keep_around(head_commit_sha)
+      repo.keep_around(base_commit_sha)
+    end
   end
 end