Allow forwarding metadata from the top-level extractor to all children
if 'parent-directory' is enabled for all extractors along the way.
For example 'reddit' -> 'gfycat' -> 'redgifs'
follow-up to 9c29fc4e
Prevent a "race" between initializing 'pathfmt' and 'hooks',
and receiving a signal in between (e.g. ctrl+c),
which would then crash in 'handle_finalize()'.
Separating the archive check from pathfmt.exists() in b5243297
had some unintended side effects.
It is also not possible to monkey-patch a dunder method like
__contains__ because of the special method lookup that gets
performed for them.
Instead of one 'postprocessors' setting overwriting all others lower
in the hierarchy, all postprocessors along the config path will now
get collected into one big list.
For example '--mtime-from-date' will therefore no longer cause
other postprocessor settings in a config file to get ignored.
Wrap all loggers used by job, extractor, downloader, and postprocessor
objects into a (custom) LoggerAdapter that provides access to the
underlying job, extractor, pathfmt, and kwdict objects and their
properties.
__init__() signatures for all downloader and postprocessor classes have
been changed to take the current Job object as their first argument,
instead of the current extractor or pathfmt.
(#574, #575)
otherwise the next call to download() with a fallback URL could see
the partially downloaded "remains" from the previous, failed download
attempt and "continue" it, writing the second half of a potentially
different version of that file.
… except ENOSPC (No space left on device), since there is no reason to
continue downloading in that case.
All other errors that would prevent downloading data and writing it to
disk get already raised during directory creation and are therefore not
checked here.
Mike Fährmann