We were over-enthusiastic when introducing --no-config into the
autocompletions. When autocompleting profiles, you actually need the
config, because that's where the profiles come from.
zsh is untested - I don't use it.
Reading the config when we're just interested in the option list
(not sure why mpv does that anyway) only has the potential to mess
this process up when it prints errors or the user has funny options
like msg-level or log-file set, so avoid doing so.
If bash_completion wasn't installed, _filedir wouldn't be defined which
led to all filename-based completions to error out. Specifically
autocompletion would fail when a filename was expected and when
bash_completion wasn't installed. Now we fall back to `compgen -f` if
_filedir fails. According to _filedir's comments, compgen doesn't
handle files with spaces well, but it is still better to complete most
files than none.
The bash completion seems to be working decently at this point, so I
feel comfortable caching the options output to improve the performance
of the completion.
Right now we are generating the fully option list before doing
anything else. That makes filename completion significantly slower
than it was before, for no gain. It's easy to only generate the
option list when it's actually needed.
I also know I could additionally cache the option list across
invocations, but I'm not doing that yet to make testing easier.
While we've had a zsh completion script for a while, we haven't had
one for bash. This one is reasonably comprehensive, although there are
improvements one could imagine for certain options.
