Check for private key when encryption is set

TODO.md

@@ -12,7 +12,6 @@
 
 ## Usability
 * Verbosity control
-* Check for private key when encryption is set
 * Display backup name and path on backup integrity error
 * Better control over what is checked in `check` subcommand
 * Nice error when remote storage is not mounted

src/repository/mod.rs

@@ -167,6 +167,9 @@ impl Repository {
     #[inline]
     pub fn set_encryption(&mut self, public: Option<&PublicKey>) {
         if let Some(key) = public {
+            if !self.crypto.lock().unwrap().contains_secret_key(key) {
+                warn!("The secret key for that public key is not stored in the repository.")
+            }
             let mut key_bytes = Vec::new();
             key_bytes.extend_from_slice(&key[..]);
             self.config.encryption = Some((EncryptionMethod::Sodium, key_bytes.into()))