New directory from interface on existing branch

Summary

With !8427 (merged) We solved the problem to create a new file on an existing branch. But the same problem persists with the new_directory form.

Steps to reproduce

• go to repository page
• click on new directory button
• select a target branch different than the source branch

You'll see Branch already existserror

Relevant logs and/or screenshots

This:

Will give this error:

Possible fixes

The fix should be the same as in !8427 (merged) to set @ref=@target_branch if branch_exists