Bug 136577

Currently, the script assumes that the reference file originates in a subdirectory of the test file's parent directory and it is imported up N levels to be the same directory as the test. In this (most common) case, the script removes relpath from its support file paths upon import. This won't work if the reference file originated in a directory above the test file and is imported down N levels. This scenario occurs many times in the CSS test repo, but it happens to be one single shared reference file that many of the css21 tests share from a common ancestor directory. In all of these cases, the original ref file and the test file's parent dir both have the same relative path to the ref file's support file, so the new location of the ref file is a lateral move and everything 'just works'. Ideally, the import script should do the right thing wherever the the ref fileorginates, but this is an edge case and highly unlikely.