feat: added clap shell completion and implemented Default trait on Args

- added build.rs: cargo will generate shell completion for bash, zsh,
fish and elvish on source change
- implemented Default trait on Args: Now we can write tests without all
those unnecessary args by replacing them with ..Default::default()

.gitignore

@@ -1,4 +1,7 @@
 /target
 
 # Generated by `oranda generate ci`
-public/
+public/
+rust-toolchain.toml
+flake.nix
+flake.lock

Cargo.toml

@@ -13,6 +13,7 @@ path = "src/main.rs"
 [dependencies]
 blake2 = "0.10.6"
 clap = { version = "4.5.23", features = ["derive"] }
+clap_complete = "4.5.40"
 console = "0.15.8"
 digest = "0.10.7"
 eyre = "0.6.12"
@@ -33,6 +34,11 @@ tracing-subscriber = { version = "0.3.19", features = ["env-filter"] }
 rand = "0.8.5"
 tempfile = "3.14.0"
 
+[build-dependencies]
+clap = { version = "4.5.23", features = ["derive"] }
+clap_complete = "4.5.40"
+clap_complete_nushell = "4.5.4"
+
 # The profile that 'dist' will build with
 [profile.dist]
 inherits = "release"