message: Fix errors with cli-common feature but not plugin
  ReadError::MissingPlugin is disabled when the plugin feature is not
  enabled. However, it was used in age/src/cli_common.rs without being
  guarded behind a compiler condition.
  This causes a compile error with the cli-common feature enabled, but not
  the plugin feature.
diff: @@ -138,6 +138,8 @@ pub fn read_identities(
  }
  Err(_) => (),
  }
  + // IdentityFileEntry::into_identity will never return a MissingPlugin error
  + // when plugin feature is not enabled.
  // Try parsing as multiple single-line age identities.
  let identity_file =
  @@ -147,14 +149,23 @@ pub fn read_identities(
  })?;
  for entry in identity_file.into_identities() {
  - identities.push(entry.into_identity(UiCallbacks).map_err(|e| match e {
  + let entry = entry.into_identity(UiCallbacks);
  +
  + #[cfg(feature = "plugin")]
  + let entry = entry.map_err(|e| match e {
  + #[cfg(feature = "plugin")]
  crate::DecryptError::MissingPlugin { binary_name } => {
  ReadError::MissingPlugin { binary_name }
  }
  // DecryptError::MissingPlugin is the only possible error kind returned by
  // IdentityFileEntry::into_identity.
  _ => unreachable!(),
  - })?);
  + })?;
  +
  + #[cfg(not(feature = "plugin"))]
  + let entry = entry.unwrap();
  +
  + identities.push(entry);
  }
  }
  