Do not warn twice (and incorrectly so) about the same issue in do_extract.
When pkg add fails and we try to clean up what we may have installed
already, be silent about failures doing so (since things may not have
been installed actually).

Change the force parameter of pkg_delete_files() from a boolean to a
tri-state on the implementation side and a add bit of documentation.
Duplicate the body of the utstring when returning it

Otherwise utstring_free will free it.
Wording
Better format new recommanded repository configuration format