[examples_redesign] Introduce example_cli package

This is the equivalent of `keychain_tracker_example_cli` that works with
the redesigned structures.

crates/chain/src/chain_data.rs

@@ -16,6 +16,13 @@ pub enum ObservedAs<A> {
     Unconfirmed(u64),
 }
 
+impl<A> ObservedAs<A> {
+    /// Returns whether [`ObservedAs`] is confirmed or not.
+    pub fn is_confirmed(&self) -> bool {
+        matches!(self, Self::Confirmed(_))
+    }
+}
+
 impl<A: Clone> ObservedAs<&A> {
     pub fn cloned(self) -> ObservedAs<A> {
         match self {

crates/chain/src/chain_oracle.rs

@@ -19,4 +19,7 @@ pub trait ChainOracle {
         block: BlockId,
         chain_tip: BlockId,
     ) -> Result<Option<bool>, Self::Error>;
+
+    /// Get the best chain's chain tip.
+    fn get_chain_tip(&self) -> Result<Option<BlockId>, Self::Error>;
 }

crates/chain/src/indexed_tx_graph.rs

@@ -203,6 +203,15 @@ impl<A: Anchor, IA: Append> Append for IndexedAdditions<A, IA> {
     }
 }
 
+impl<A, IA: Default> From<Additions<A>> for IndexedAdditions<A, IA> {
+    fn from(graph_additions: Additions<A>) -> Self {
+        Self {
+            graph_additions,
+            ..Default::default()
+        }
+    }
+}
+
 /// Represents a structure that can index transaction data.
 pub trait Indexer {
     /// The resultant "additions" when new transaction data is indexed.

crates/chain/src/local_chain.rs

@@ -34,6 +34,10 @@ impl ChainOracle for LocalChain {
             },
         )
     }
+
+    fn get_chain_tip(&self) -> Result<Option<BlockId>, Self::Error> {
+        Ok(self.tip())
+    }
 }
 
 impl AsRef<BTreeMap<u32, BlockHash>> for LocalChain {