Make librespot able to parse environment variables for options and flags.
To avoid name collisions environment variables must be prepended with `LIBRESPOT_` so option/flag `foo-bar` becomes `LIBRESPOT_FOO_BAR`.
Verbose logging mode (`-v`, `--verbose`) logs all parsed environment variables and command line arguments (credentials are redacted).
This makes `--device ?` only show compatible devices (ones that support 2 ch 44.1 Interleaved) and it shows what `librespot` format(s) they support.
This should be more useful to users as the info maps directly to `librespot`'s `--device` and `--format` options.
* Don't panic when parsing options. Instead list valid values and exit.
* Get rid of needless .expect in playback/src/audio_backend/mod.rs.
* Enforce reasonable ranges for option values (breaking).
* Don't evaluate options that would otherwise have no effect.
* Add pub const MIXERS to mixer/mod.rs very similar to the audio_backend's implementation. (non-breaking though)
* Use different option descriptions and error messages based on what backends are enabled at build time.
* Add a -q, --quiet option that changed the logging level to warn.
* Add a short name for every flag and option.
* Note removed options.
* Other misc cleanups.
While `Xoshiro256+` is faster on 64-bit, it has low linear complexity in the
lower three bits, which *are* used when generating dither.
Also, while `Xoshiro128StarStar` access one less variable from the heap,
multiplication is generally slower than addition in hardware.
* When autoplay is disabled, then loop back to the first track
instead of 10 tracks back. Continue or stop playing depending
on the state of the repeat button.
* When autoplay is enabled, then extend the playlist *after* the
last track. #844 broke this such that the last track of an album
or playlist was never played.
Fixes: #434
* Make error messages more consistent and concise.
* `impl From<AlsaError> for io::Error` so `AlsaErrors` can be thrown to player as `io::Errors`. This little bit of boilerplate goes a long way to simplifying things further down in the code. And will make any needed future changes easier.
* Bonus: handle ALSA backend buffer sizing a little better.
