feature: cli completions

[XyLyXyRR]

Hi, there. I just impl completions for this project.

But there is a little awkward. clap 3-beta doesn't have 'completions' right now, so I downgrade to clap 2. (x
And a little ugly code to handle these differences.

Thank you.

[ajeetdsouza]

Hey @XyLyXyRR, thanks for your work on this!

clap v3 does actually support shell completions. I'm not sure how good they are, but I suppose it wouldn't hurt to include a version-controlled directory with autogenerated completions from clap while we test them out. Unfortunately, that would require reworking your current implementation.

The way I would go about this is:

• Use the generate_to function in build.rs to generate completions at compile time. The way it's done is admittedly a little hacky, but the exact procedure is given in the documentation.
• The include!("src/cli.rs"); line requires the whole app to be specified in a single file with no crate dependencies.
  • Move all the current App-related structs out into src/app.rs.
  • Rename crate::cmd::Cmd to crate::run::Run.
  • Let crate::run::<subcommand> import from crate::app::<subcommand>.
• Use clap_generate::generate_to to write completions to contrib/completions. We can move it out of contrib once it's sufficiently stable. Use include!(src/app.rs); for getting the struct, and convert the struct to an app using into_app.

PS: the issue you linked actually refers to completions for z using zoxide query -l, which would not be fixed by this PR, so I've removed it from the PR description.

[XyLyXyRR]

Hey @ajeetdsouza, I finished it.

Have a good day!

[ajeetdsouza]

This is great, thank you!