implement sensible handling of checksum fields in .changes and .dsc

implement sensible handling of checksum fields in .changes and .dsc

2008-08-28  Philipp Kern  <pkern@debian.org>

	* daklib/utils.py (check_hashes): adapt to different API, check
	sizes separately

	* daklib/utils.py (parse_changes, parse_deb822): refactor
	the string-based logic of parse_changes into a new function
	parse_deb822; parse_changes itself remains file-based

	* daklib/utils.py (hash_key): gives the key of a hash in the
	files dict

	* daklib/utils.py (create_hash, check_size): made more readable

	* daklib/utils.py (check_hash): just check the hashes and complain
	about missing checksums

	* daklib/utils.py (check_hash_fields): function to reject unknown
	checksums fields

	* daklib/utils.py (_ensure_changes_hash, _ensure_dsc_hash): helper
	functions for ensure_hashes; check their corresponding manifests'
	hashes

	* daklib/utils.py (ensure_hashes): retrieve the checksums fields
	from the original filecontents blob so that they do not need to
	be present in the .dak; refactored the actual checks by calling
	the aforementioned helper functions

	* daklib/utils.py (parse_checksums): parse a given checksums field
	in a manifest and insert the values found into the files dict,
	checking the file sizes on the way