feat: unpin a server back to trust on first use

core/src/store.rs

@@ -283,6 +283,15 @@ impl Store {
             .and_then(|k| k.try_into().ok()))
     }
 
+    /// Removes a pin: the settings screen's unpin, the inverse of
+    /// `pin_server`. The next session against that host is trust on first
+    /// use again (sec 4, sec 8).
+    pub fn unpin_server(&self, host: &str) -> Result<(), Error> {
+        self.db()
+            .execute("DELETE FROM servers WHERE host = ?1", params![host])?;
+        Ok(())
+    }
+
     /// Every pin, host and key, ordered by host — the export's server map.
     pub fn pins(&self) -> Result<Vec<(String, [u8; KEY_LEN])>, Error> {
         let db = self.db();
@@ -881,6 +890,16 @@ mod tests {
         assert_eq!(store.history("alice@example.org").unwrap(), [([9u8; 32], 42)]);
     }
 
+    #[test]
+    fn unpin_returns_to_trust_on_first_use() {
+        let store = temp_store("unpin");
+        store.pin_server("example.org", &[1u8; KEY_LEN]).unwrap();
+        store.unpin_server("example.org").unwrap();
+        assert_eq!(store.server_pin("example.org").unwrap(), None);
+        // Unpinning what was never pinned is not an error.
+        store.unpin_server("never.example.org").unwrap();
+    }
+
     #[test]
     fn kept_survives_the_folder_listing() {
         let store = temp_store("kept");