[MereInterest]

Thank you, and that's probably a cleaner solution than what I've been doing. I've been making a temp directory, hard-linking each file to the appropriate location within that temp directory, then running docker from within that location.

Though, either approach does have the tremendous downside of needing to maintain two entirely separate lists of the same set of files. It needs to be maintained both in the Dockerfile, and in the arguments provided to tar.