* upgrade to partftpy 0.4.0
* workarounds for buggy clients/servers
* improved ipv6 support, especially on macos
* improved robustness on unreliable networks
* make `--tftp4` separate from `--ftp4`
only keep characters `>+-*` if there's less than three of them,
and discard entire prefix if there's more
markdown spec only cares about exactly-one or three-or-more, but
let's keep pairs in case anyone use that as unconventional markup
when there was more than ~700 active connections,
* sendfile (non-https downloads) could fail
* mdns and ssdp could fail to reinitialize on network changes
...because `select` can't handle FDs higher than 512 on windows
(1024 on linux/macos), so prefer `poll` where possible (linux/macos)
but apple keeps breaking and unbreaking `poll` in macos,
so use `--no-poll` if necessary to force `select` instead
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
use sigmasks to block SIGINT, SIGTERM, SIGUSR1 from all other threads
also initiate shutdown by calling sighandler directly,
in case this misses anything and that is still unreliable
(discovered by `--exit=idx` being noop once in a blue moon)
* template-based title formatting
* picture embeds are no longer ant-sized
* `--og-color` sets accent color; default #333
* `--og-s-title` forces default title, ignoring e2t
* add a music indicator to song titles because discord doesn't
currently only being used to workaround discord discarding
query strings in opengraph tags, but i'm sure there will be
plenty more wonderful usecases for this atrocity
if a given filesystem were to disappear (e.g. removable storage)
followed by another filesystem appearing at the same location,
this would not get noticed by up2k in a timely manner
fix this by discarding the mtab cache after `--mtab-age` seconds and
rebuild it from scratch, unless the previous values are definitely
correct (as indicated by identical output from `/bin/mount`)
probably reduces windows performance by an acceptable amount
