chain get: @Hu: for uvaring hamt keys

cli/chain.go

@@ -433,6 +433,8 @@ var chainGetCmd = &cli.Command{
    Note:
    You can use special path elements to traverse through some data structures:
    - /ipfs/[cid]/@H:elem - get 'elem' from hamt
+   - /ipfs/[cid]/@Hi:123 - get varint elem 123 from hamt
+   - /ipfs/[cid]/@Hu:123 - get uvarint elem 123 from hamt
    - /ipfs/[cid]/@Ha:t01 - get element under Addr(t01).Bytes
    - /ipfs/[cid]/@A:10 - get 10th amt element
 `,

node/impl/full/chain.go

@@ -285,6 +285,17 @@ func resolveOnce(bs blockstore.Blockstore) func(ctx context.Context, ds ipld.Nod
 			names[0] = "@H:" + ik.Key()
 		}
 
+		if strings.HasPrefix(names[0], "@Hu:") {
+			i, err := strconv.ParseUint(names[0][4:], 10, 64)
+			if err != nil {
+				return nil, nil, xerrors.Errorf("parsing int64: %w", err)
+			}
+
+			ik := adt.UIntKey(i)
+
+			names[0] = "@H:" + ik.Key()
+		}
+
 		if strings.HasPrefix(names[0], "@H:") {
 			cst := cbor.NewCborStore(bs)