Make Repository#blob_data_at a public method

This reduces conflicts with EE, where it is public because it is
called in ee/lib/gitlab/ci/external/file/local.rb.

app/models/repository.rb

@@ -957,6 +957,14 @@ class Repository
                                        remote_branch: merge_request.target_branch)
   end
+  def blob_data_at(sha, path)
+    blob = blob_at(sha, path)
+    return unless blob
+
+    blob.load_all_data!
+    blob.data
+  end
+
   def squash(user, merge_request)
     raw.squash(user, merge_request.id, branch: merge_request.target_branch,
                                        start_sha: merge_request.diff_start_sha,
@@ -979,14 +987,6 @@ class Repository
     ::Commit.new(commit, @project) if commit
   end
-  def blob_data_at(sha, path)
-    blob = blob_at(sha, path)
-    return unless blob
-
-    blob.load_all_data!
-    blob.data
-  end
-
   def cache
     @cache ||= Gitlab::RepositoryCache.new(self)
   end