* backend/enhanced: start with absolute config path
We recently started normalizing the config path before all "command"
operations, which was necessary for consistency but had unexpected
consequences for remote backend operations, specifically when a vcs root
with a working directory are configured.
This PR de-normalizes the path back to an absolute path.
* Check the error and add a test
It turned out all required logic was already present, so I just needed to add a test for this specific use case.
89eeaed0a0