- Spack's core package interface was previously overly stateful, in that
calling methods like `do_stage()` could change your working directory.
- This removes Stage's `chdir` and `chdir_to_source` methods and replaces
their usages with `with working_dir(stage.path)` and `with
working_dir(stage.source_path)`, respectively. These ensure the
original working directory is preserved.
- This not only makes the API more usable, it makes the tests more
deterministic, as previously a test could leave the current working
directory in a bad state and cause subsequent tests to fail
mysteriously.
c14f2dc7b4