* Add automatic shell completion generation.
Add automatic generation of shell completion scripts for various shells
(the ones supported by `clap_complete`). The scripts can be generated
using the `generate-shell-completion` xtask, which outputs the shell
script to stdout.
* Improve shell completion generation xtask.
General improvements to both the shell completion generation as well as
the xtask package itself. Update the README to match the new additions.
* Add manpage generation.
* Hide xtask compilation info.
This changes the default behavior of the `cargo run` command for xtasks
to hide the compilation info. This makes sense as xtask's are run as a
program, and showing the compilation info every time clutters stdout
with unrelated info.
* Move ncspot's `clap::Command` to `lib.rs`.
Moving the `clap::Command` used internally by ncspot to a library allows
it to be easily shared between different packages (xtask and ncspot
itself).
This commit also reworks the xtasks to use clap for parsing the xtask
arguments, which simplifies writing new xtasks.
* Make `generate-manpage` `--output` optional.
When more xtasks get added, it would make sense to have a `generate-all`
subcommand that executes all xtasks, which wouldn't be able to have
options for every separate subcommand. Therefore the `output` argument
should be optional, and by default output to the `misc` directory which
contains extra metadata files already.
* Add packaging info to `README.md`.
Update the README to include information for packagers. The information
includes provided files as well as info on how to generate some of them.
