* Add "before_choose_candidate" unit tests (PromptChoicesTest), containing
tests for checking the addition of choices to ui.input_options (album and
singletons), conflict resolution, and callback handling (regular and with
return value).
* Add changelog and query.rst documentation entries for the usage of negated
queries.
* Cleanup NotQuery class as suggested during code review (PEP conforming
docstring, clarification on empty clause match behaviour).
* Revise the NotQuery syntax, replacing the '¬' character with '^'. Fix tests
to conform to this change, and cleanup the PARSE_QUERY_PART_REGEX.
* Modify parse_query_part() docstring to mention the negate parameter on the
returned tuple, and added an example.
* Add tests to NotQueryTest for testing the results of using queries with
negation.
* Fix issue on test_dbcore due to the modifications on the tuple returned by
parse_query_part (the number of elements was changed from 3 to 4).
* Modify NotQuery so it subclasses Query instead of MutableCollectionQuery.
* Update instances where NotQuery objects are created on tests and queryparse,
as NotQuery expects a single Query as a parameter to the constructor instead of
a list of Queries.
* Add support for user friendly "not" operator in queries without requiring to
use regular expressions, via adding NotQuery to beets.dbcore.query.
* Update the prefix list at library.parse_query_parts() and the query parsing
mechanisms in order to create a NotQuery when the prefix is found.
* Add two TestCases, NotQueryMatchTest as the negated version of MatchTest, and
the more generic NotQueryTest for testing the integration of the NotQuery with
the rest of the existing Query subclasses.
* Update test for extra fields in edited yaml, allowing the user to add fields
while editing. Rename the test to test_single_edit_add_field to reflect its
purpose more accurately.
* Update unit tests in order to reflect the changes on the last refactor of
edit.py (patch edit.edit instead of EditPlugin.get_editor, revise stdin strings
to match current version, remove TODO on docstrings from malformed and invalid
yaml tests).
* Add tests for executing the command with album queries (-a), testing the edit
of album and albumartist fields.
* Revise invalid and malformed yaml tests so they return a failure instead of
an error.
* Modify existing tests in order to explicitely check for differences (or lack
of) in the items fields, with the intention to ensure that no unintended changes
slip through.
* Added tests for modifying a single item from a list of items, and for editing
the album field of the items (stub for discussing whether the actual album
should be updated, etc).
