feat: add completions (#97)

tests/cli.rs

@@ -0,0 +1,32 @@
+//! Run cli with different args, not starting a server
+
+mod fixtures;
+
+use assert_cmd::prelude::*;
+use clap::ValueEnum;
+use clap_complete::Shell;
+use fixtures::Error;
+use std::process::Command;
+
+#[test]
+/// Show help and exit.
+fn help_shows() -> Result<(), Error> {
+    Command::cargo_bin("dufs")?.arg("-h").assert().success();
+
+    Ok(())
+}
+
+#[test]
+/// Print completions and exit.
+fn print_completions() -> Result<(), Error> {
+    // let shell_enums = EnumValueParser::<Shell>::new();
+    for shell in Shell::value_variants() {
+        Command::cargo_bin("dufs")?
+            .arg("--completions")
+            .arg(shell.to_string())
+            .assert()
+            .success();
+    }
+
+    Ok(())
+}