Add is_tty field to Context

This patch adds the is_tty field to the Context struct that indicates
whether stdout is a TTY.  This allows us to use TTY features like moving
the cursor in our output.

CHANGELOG.md

@@ -2,6 +2,7 @@ Unreleased
 ----------
 - Added the `fill` command that fills the SD card of a Nitrokey Storage device
  with random data
+ - Added the `termion` dependency in version `1.5.5`
 - Added SD card usage information to the output of the `status` command for
  Storage devices
 

Cargo.toml

@@ -61,6 +61,9 @@ features = ["derive"]
 version = "0.3.17"
 default-features = false
 
+[dependencies.termion]
+version = "1.5.5"
+
 [dependencies.toml]
 version = "0.5.6"
 

src/main.rs

@@ -98,6 +98,8 @@ pub struct Context<'io> {
  pub stdout: &'io mut dyn io::Write,
  /// The `Write` object used as standard error throughout the program.
  pub stderr: &'io mut dyn io::Write,
+ /// Whether `stdout` is a TTY.
+ pub is_tty: bool,
  /// The admin PIN, if provided through an environment variable.
  pub admin_pin: Option<ffi::OsString>,
  /// The user PIN, if provided through an environment variable.
@@ -118,14 +120,20 @@ pub struct Context<'io> {
 }
 
 impl<'io> Context<'io> {
- fn from_env<O, E>(stdout: &'io mut O, stderr: &'io mut E, config: config::Config) -> Context<'io>
+ fn from_env<O, E>(
+ stdout: &'io mut O,
+ stderr: &'io mut E,
+ is_tty: bool,
+ config: config::Config,
+ ) -> Context<'io>
  where
  O: io::Write,
  E: io::Write,
  {
  Context {
  stdout,
  stderr,
+ is_tty,
  admin_pin: env::var_os(NITROCLI_ADMIN_PIN),
  user_pin: env::var_os(NITROCLI_USER_PIN),
  new_admin_pin: env::var_os(NITROCLI_NEW_ADMIN_PIN),
@@ -154,8 +162,9 @@ fn main() {
 
  let rc = match config::Config::load() {
  Ok(config) => {
+ let is_tty = termion::is_tty(&stdout);
  let args = env::args().collect::<Vec<_>>();
- let ctx = &mut Context::from_env(&mut stdout, &mut stderr, config);
+ let ctx = &mut Context::from_env(&mut stdout, &mut stderr, is_tty, config);
 
  run(ctx, args)
  }

src/tests/mod.rs

@@ -99,6 +99,7 @@ impl Nitrocli {
  let ctx = &mut crate::Context {
  stdout: &mut stdout,
  stderr: &mut stderr,
+ is_tty: false,
  admin_pin: self.admin_pin.clone(),
  user_pin: self.user_pin.clone(),
  new_admin_pin: self.new_admin_pin.clone(),