wpylib.file.file_utils since they are not directly related to shell:
- file_exists_nonempty
- is_executable_file
- dirname2
- relpath
- path_split_all
- list_dir_entries
These are new API functions, so hopefully their changes would not
affect many existing scripts.
* Added support for xz-compressed tar in untar() routine. Untested.
* Documentation updates.
recursively all through directories (no symlink following), to collect
all subdirectories that satisfy the test criteria defined in the
testdir() function argument.