Fix Error 500 when creating a merge request that contains an image that was deleted and added

Steps to reproduce:

1. Start with a repo with an image
2. Add a commit to delete the image
3. Add another commit to replace the image with another image

In a diff comparison, we really just compare about what the image was before the diff, not
the direct parent of the last commit. This MR fixes that.

Closes #3893, gitlab-org/gitlab-ee#678

Signed-off-by: Rémy Coutable <remy@rymai.me>

1 files changed, 24 insertions, 0 deletions

diff --git a/spec/lib/gitlab/diff/file_spec.rb b/spec/lib/gitlab/diff/file_spec.rb
index 0650cb291e5..38475792d93 100644
--- a/spec/lib/gitlab/diff/file_spec.rb
+++ b/spec/lib/gitlab/diff/file_spec.rb
@@ -46,4 +46,28 @@ describe Gitlab::Diff::File, lib: true do
       expect(diff_file.collapsed?).to eq(false)
     end
   end
+
+  describe '#old_content_commit' do
+    it 'returns base commit' do
+      old_content_commit = diff_file.old_content_commit
+
+      expect(old_content_commit.id).to eq('6f6d7e7ed97bb5f0054f2b1df789b39ca89b6ff9')
+    end
+  end
+
+  describe '#old_blob' do
+    it 'returns blob of commit of base commit' do
+      old_data = diff_file.old_blob.data
+
+      expect(old_data).to include('raise "System commands must be given as an array of strings"')
+    end
+  end
+
+  describe '#blob' do
+    it 'returns blob of new commit' do
+      data = diff_file.blob.data
+
+      expect(data).to include('raise RuntimeError, "System commands must be given as an array of strings"')
+    end
+  end
 end