It really didn't make sense to me before I did some further research. You shouldn't have to do further research to understand this apart form reading the docs.
* Remove the RETAG-specific logic on align_album_level_fields, assuming
that the user will always make sure to have proper data on the first
item.
* Revise some docstrings and comments in order to clarify the use of
RETAG.
* Revert the changes related to allowing the album- and item-level
fields to be edited at the same time, as the increase in complexity
was deemed excesive during review.
* Modify the interactive execution so temporary Item.id's are used,
removing the extra functionality needed for dealing with both id and
path as reference fields.
* Docstrings and comments cleanup.
* Add support for editing both the item fields and the album fields in
a single YAML file, by appending an Album-like object as the front of
the objects to be edited.
* The FakeAlbum class provides that object, mimicking the original
Album behaviour and including an _apply_changes() method that propagates
the changes read from the yaml onto the Items.
* Modify edit_objects() so the flattening of the objects takes into
account the type of object, using different fields for Albums and for
Items.
* Renamed apply() to apply_() to prevent an IDE warning about reusing a
reserved built-in symbol.
* Add EditDuringImporterTest test case, covering the running of the
plugin during an import session. Includes editing the "album" field
and applying/discarding for both editing from items and editing from
a candidate; and editing and applying for singletons for both editing
from items and editing from a candidate.
* Add support for the RETAG action to SingletonImportTask.
* Modify ImportTask.align_album_level_fields() so the source of the
information is a bit more intelligent in the RETAG case instead of
always assuming the items come from applied metadata.
* Make the edit plugin return action.RETAG when invoked during an
interactive import session, making the importer handle the writing of
the tags to the files (if needed) properly.
* Move the logic relative to the "reference field" to
_set_reference_field(), simplifying a bit the functions that depend on
this field.
* Hide the "edit Candidates" choice if no candidates are found.
* Add importer "RETAG" action, to represent the case where the files
metadata has been modified by some mean other than applying metadata
(via a plugin), and as a result needs to be written to disk if the
"write" config flag is set.
* Initial draft for invoking the edit plugin during an importer session.
* Add prompt choices for editing the original file tags ("eDit") and
apply a candidate and then edit ("edit Candidates").
* Modify plugin (_get_fields, apply_data, edit_objects) so "path" can be
used as a reference field instead of "id", as the Items are not still on
the database when the plugin is invoked via the importer.
* Modify ImportTask.manipulate_files() with a temporary flag for writing
the item tags even if ASIS was selected.
