dir restructure to support more CGP (#1266)

* rerame res to chain-specs

* split polkadot-parachains dir

* rename dir parachains-common to common

Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>
Co-authored-by: Wilfried Kopp <wilfried@parity.io>
Co-authored-by: Chevdor <chevdor@users.noreply.github.com>

parachains/common/src/xcm_config.rs

@@ -0,0 +1,67 @@
+use core::marker::PhantomData;
+use frame_support::{log, weights::Weight};
+use xcm::latest::prelude::*;
+use xcm_executor::traits::ShouldExecute;
+
+//TODO: move DenyThenTry to polkadot's xcm module.
+/// Deny executing the XCM if it matches any of the Deny filter regardless of anything else.
+/// If it passes the Deny, and matches one of the Allow cases then it is let through.
+pub struct DenyThenTry<Deny, Allow>(PhantomData<Deny>, PhantomData<Allow>)
+where
+	Deny: ShouldExecute,
+	Allow: ShouldExecute;
+
+impl<Deny, Allow> ShouldExecute for DenyThenTry<Deny, Allow>
+where
+	Deny: ShouldExecute,
+	Allow: ShouldExecute,
+{
+	fn should_execute<Call>(
+		origin: &MultiLocation,
+		message: &mut Xcm<Call>,
+		max_weight: Weight,
+		weight_credit: &mut Weight,
+	) -> Result<(), ()> {
+		Deny::should_execute(origin, message, max_weight, weight_credit)?;
+		Allow::should_execute(origin, message, max_weight, weight_credit)
+	}
+}
+
+// See issue #5233
+pub struct DenyReserveTransferToRelayChain;
+impl ShouldExecute for DenyReserveTransferToRelayChain {
+	fn should_execute<Call>(
+		origin: &MultiLocation,
+		message: &mut Xcm<Call>,
+		_max_weight: Weight,
+		_weight_credit: &mut Weight,
+	) -> Result<(), ()> {
+		if message.0.iter().any(|inst| {
+			matches!(
+				inst,
+				InitiateReserveWithdraw {
+					reserve: MultiLocation { parents: 1, interior: Here },
+					..
+				} | DepositReserveAsset { dest: MultiLocation { parents: 1, interior: Here }, .. } |
+					TransferReserveAsset {
+						dest: MultiLocation { parents: 1, interior: Here },
+						..
+					}
+			)
+		}) {
+			return Err(()) // Deny
+		}
+
+		// allow reserve transfers to arrive from relay chain
+		if matches!(origin, MultiLocation { parents: 1, interior: Here }) &&
+			message.0.iter().any(|inst| matches!(inst, ReserveAssetDeposited { .. }))
+		{
+			log::warn!(
+				target: "xcm::barrier",
+				"Unexpected ReserveAssetDeposited from the relay chain",
+			);
+		}
+		// Permit everything else
+		Ok(())
+	}
+}