Obtain the API difference between two runtime nodes

[lexnv]

There are cases when nodes contain different versions of the metadata, with modified/added pallets/calls.
It would be valuable to have a tool that outputs the differences in metadata in a human-readable way.

• Full metadata inspection

> subxt-cli diff http://localhost:9933 http://localhost:9934

+ pallet XCM

• Per pallet inspection

> subxt-cli diff http://localhost:9933 http://localhost:9934 --pallet Balances
--- a/http://localhost:9933/metadata/pallet/Balances
--- b/http://localhost:9934/metadata/pallet/Balances

pub mod calls {

+ pub struct NewTransferCall {
+     pub dest: ::subxt::sp_runtime::MultiAddress<
+         ::subxt::sp_core::crypto::AccountId32,
+         (),
+     >,
+     #[codec(compact)]
+     pub value: ::core::primitive::u128,
+ }
+ impl ::subxt::Call for Transfer {
+     const PALLET: &'static str = "Balances";
+     const FUNCTION: &'static str = "transfer";
+ }

• Per call/storage/constant... inspection

> subxt-cli diff http://localhost:9933 http://localhost:9934 --pallet Balances --call NewTransferCall
--- a/http://localhost:9933/metadata/Balances/calls/NewTransferCall
--- b/http://localhost:9934/metadata/Balances/calls/NewTransferCall

pub struct NewTransferCall {
    pub dest: ::subxt::sp_runtime::MultiAddress<
-         ::subxt::sp_core::crypto::AccountId32,
+         ::subxt::sp_core::crypto::AccountId64,
        (),

[jsdw]

I like the diff style markers, but I also wonder whether the interface should be more code-based as above, or a little more human-readable. Definitely the structure of the output could do with some pondering; how can we most easily show people what the differences are?