.stowrc can be obtained from $HOME and/or the current working
directory; however only the $HOME case was tested before, because
during tests Stow was being run from $HOME.
So switch $TEST_DIR to an absolute path, create a new run_from/
subdirectory, and chdir to that before invoking any Stow code. This
allows us to test the behaviour of .stowrc in $HOME and run_from/
separately.
Why:
* Want to add a new feature to parsing of stowrc files.
* Need ability to write .stowrc files for testing without risk of
squashing existing files.
This change addresses the need by:
* Reusing logic in init_test_dirs
* init_test_dirs already creates new directory structure and overwrites
$HOME to point into /tmp.
* This commit changes init_test_dirs to point $HOME at the newly created
directory structure ($OUT_DIR) instead of /tmp.
* Grants ability to write .stowrc to $HOME without fear.
* Pointing $HOME at $OUT_DIR instead of /tmp also makes cleanup easier.
* Remove $OUT_DIR vs remove specific files in /tmp.
