Merge branch 'fix-conflict-resolution-with-corrupt-repos' into 'master'

Fix conflict resolution from corrupted upstream

Closes gitlab-ee#2128

See merge request !11298

1 files changed, 34 insertions, 8 deletions

diff --git a/lib/gitlab/conflict/file_collection.rb b/lib/gitlab/conflict/file_collection.rb
index 990b719ecfd..6e73361cad1 100644
--- a/lib/gitlab/conflict/file_collection.rb
+++ b/lib/gitlab/conflict/file_collection.rb
@@ -3,16 +3,33 @@ module Gitlab
     class FileCollection
       ConflictSideMissing = Class.new(StandardError)
 
-      attr_reader :merge_request, :our_commit, :their_commit
+      attr_reader :merge_request, :our_commit, :their_commit, :project
 
-      def initialize(merge_request)
-        @merge_request = merge_request
-        @our_commit = merge_request.source_branch_head.raw.raw_commit
-        @their_commit = merge_request.target_branch_head.raw.raw_commit
-      end
+      delegate :repository, to: :project
+
+      class << self
+        # We can only write when getting the merge index from the source
+        # project, because we will write to that project. We don't use this all
+        # the time because this fetches a ref into the source project, which
+        # isn't needed for reading.
+        def for_resolution(merge_request)
+          project = merge_request.source_project
+
+          new(merge_request, project).tap do |file_collection|
+            project.
+              repository.
+              with_repo_branch_commit(merge_request.target_project.repository, merge_request.target_branch) do
+
+              yield file_collection
+            end
+          end
+        end
 
-      def repository
-        merge_request.project.repository
+        # We don't need to do `with_repo_branch_commit` here, because the target
+        # project always fetches source refs when creating merge request diffs.
+        def read_only(merge_request)
+          new(merge_request, merge_request.target_project)
+        end
       end
 
       def merge_index
@@ -55,6 +72,15 @@ Merge branch '#{merge_request.target_branch}' into '#{merge_request.source_branc
 #{conflict_filenames.join("\n")}
 EOM
       end
+
+      private
+
+      def initialize(merge_request, project)
+        @merge_request = merge_request
+        @our_commit = merge_request.source_branch_head.raw.raw_commit
+        @their_commit = merge_request.target_branch_head.raw.raw_commit
+        @project = project
+      end
     end
   end
 end