Fix resolving conflicts on forks21459-resolving-merge-conflicts-from-a-forked-repo-through-ui

Forks may not be up-to-date with the target project, and so might not
contain one of the parent refs in their repo. Fetch this if it isn't
present.

1 files changed, 15 insertions, 1 deletions

diff --git a/app/services/merge_requests/resolve_service.rb b/app/services/merge_requests/resolve_service.rb
index adc71b0c2bc..bd8b9f8cfd4 100644
--- a/app/services/merge_requests/resolve_service.rb
+++ b/app/services/merge_requests/resolve_service.rb
@@ -1,11 +1,14 @@
 module MergeRequests
   class ResolveService < MergeRequests::BaseService
-    attr_accessor :conflicts, :rugged, :merge_index
+    attr_accessor :conflicts, :rugged, :merge_index, :merge_request
 
     def execute(merge_request)
       @conflicts = merge_request.conflicts
       @rugged = project.repository.rugged
       @merge_index = conflicts.merge_index
+      @merge_request = merge_request
+
+      fetch_their_commit!
 
       conflicts.files.each do |file|
         write_resolved_file_to_index(file, params[:sections])
@@ -27,5 +30,16 @@ module MergeRequests
       merge_index.add(path: our_path, oid: rugged.write(new_file, :blob), mode: file.our_mode)
       merge_index.conflict_remove(our_path)
     end
+
+    # If their commit (in the target project) doesn't exist in the source project, it
+    # can't be a parent for the merge commit we're about to create. If that's the case,
+    # fetch the target branch ref into the source project so the commit exists in both.
+    #
+    def fetch_their_commit!
+      return if rugged.include?(conflicts.their_commit.oid)
+
+      remote = rugged.remotes.create_anonymous(merge_request.target_project.repository.path_to_repo)
+      remote.fetch(merge_request.target_branch)
+    end
   end
 end