prompt for password if none is given

This shows a password prompt, if neither the `--password-file` or
`--password-command` option is given **and** the `RESTIC_PASSWORD` env
variable is unset.

There's no way to hand over the password to restic as a CLI parameter,
so we use the `RESTIC_PASSWORD` env variable under the hood to set it
instead. The env variable is only valid for the restic process we call
internally, so the next time redu is run, it'll prompt for the password
again.

Cargo.toml

@@ -26,6 +26,7 @@ ratatui = { version = "0.27", features = [
         "unstable-rendered-line-info",
         "unstable-widget-ref",
 ] }
+rpassword = "7.3.1"
 rusqlite = { version = "0.32", features = ["bundled", "functions", "trace"] }
 scopeguard = "1"
 serde = { version = "1", features = ["derive"] }

src/args.rs

@@ -1,6 +1,9 @@
+use std::{env, io::Write};
+
 use clap::{ArgGroup, Parser};
 use log::LevelFilter;
 use redu::restic::Repository;
+use rpassword::read_password;
 
 use crate::restic::Password;
 
@@ -33,7 +36,11 @@ impl Args {
             } else if let Some(str) = cli.restic_password {
                 Password::Plain(str)
             } else {
-                unreachable!("Error in Config: neither password_command nor password_file found. Please open an issue if you see this.")
+                let pwd = Self::read_password_from_stdin();
+                // There's no way to hand over the password to restic directly, so we use the env
+                // variable instead.
+                env::set_var("RESTIC_PASSWORD", &pwd);
+                Password::Plain(pwd)
             },
             parallelism: cli.parallelism,
             log_level: match cli.verbose {
@@ -44,6 +51,13 @@ impl Args {
             no_cache: cli.no_cache,
         }
     }
+
+    fn read_password_from_stdin() -> String {
+        print!("enter password for repository: ");
+        // Console output is line buffered, so we need to flush to show the message.
+        _ = std::io::stdout().flush();
+        read_password().unwrap()
+    }
 }
 
 /// This is like ncdu for a restic respository.
@@ -83,11 +97,6 @@ impl Args {
         .required(true)
         .args(["repo", "repository_file"]),
 ))]
-#[command(group(
-    ArgGroup::new("password")
-        .required(true)
-        .args(["password_command", "password_file", "restic_password"]),
-))]
 struct Cli {
     #[arg(short = 'r', long, env = "RESTIC_REPOSITORY")]
     repo: Option<String>,