* if free ram on startup is less than 2 GiB,
use smaller chunks for parallel file hashing
* if --th-max-ram is lower than 0.25 (256 MiB),
print a warning that thumbnails will not work
* make thumbnail cleaner immediately do a sweep on startup,
forgetting any failed conversions so they can be retried
in case the memory limit was increased since last run
audio extraction happens serverside to opus or mp3
depending on browser support
remuxing (extracting audio without transcoding)
is currently not supported, and is not planned
metadata is no longer discarded when transcoding to opus or mp3;
this was a good idea back when the transcodes were only used by
the webplayer, but now that folders can be batch-downloaded with
on-the-fly transcoding, it makes sense to keep most of the tags
individual tags are discarded if its value exceeds 1023 letters
this should mainly affect the following:
* traktor beatmaps, size usually somewhere around 100 KiB
* non-standard cover-art embeddings, size around 250 KiB
* XMP (project data from adobe premiere), around 48 KiB
some clients (clonezilla-webdav) rapidly create and delete files;
this fails if copyparty is still hashing the file (usually the case)
and the same thing can probably happen due to antivirus etc
add global-option --rm-retry (volflag rm_retry) specifying
for how long (and how quickly) to keep retrying the deletion
default: retry for 5sec on windows, 0sec (disabled) on everything else
because this is only a problem on windows
this carries some intentional side-effects; each thumbnail format will
now be stored in its own subfolder under .hist/th/ making cleanup more
effective (jpeg and webm are dropped separately)
