[block-ref-repair] mention garage block repair-rc in documentation

doc/book/operations/durability-repairs.md

@@ -141,4 +141,7 @@ blocks may still be held by Garage. If you suspect that such corruption has occu
 in your cluster, you can run one of the following repair procedures:
 
 - `garage repair versions`: checks that all versions belong to a non-deleted object, and purges any orphan version
-- `garage repair block_refs`: checks that all block references belong to a non-deleted object version, and purges any orphan block reference (this will then allow the blocks to be garbage-collected)
+
+- `garage repair block-refs`: checks that all block references belong to a non-deleted object version, and purges any orphan block reference (this will then allow the blocks to be garbage-collected)
+
+- `garage repair block-rc`: checks that the reference counters for blocks are in sync with the actual number of non-deleted entries in the block reference table

src/garage/cli/util.rs

@@ -451,7 +451,7 @@ pub fn print_block_info(
 	if refcount != nondeleted_count {
 		println!();
 		println!(
-			"Warning: refcount does not match number of non-deleted versions (see issue #644)."
+			"Warning: refcount does not match number of non-deleted versions, you should try `garage repair block-rc`."
 		);
 	}
 }