Keep old migrations around

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Author: ggwpez

runtime/kusama/src/lib.rs

@@ -1475,14 +1475,16 @@ impl Get<Perbill> for NominationPoolsMigrationV4OldPallet {
 
 /// All migrations that will run on the next runtime upgrade.
 ///
-/// Should be cleared after every release.
+/// This contains the combined migrations of the last 10 releases. It allows to skip runtime
+/// upgrades in case governance decides to do so.
 #[allow(deprecated)]
 pub type Migrations = (
+	// 0.9.40
 	pallet_nomination_pools::migration::v4::MigrateToV4<
 		Runtime,
 		NominationPoolsMigrationV4OldPallet,
 	>,
-	// NOTE: If we don't propose 0.9.40 on chain; these two can be replaced with `MigrateV3ToV5`.
+	// Unreleased - add new migrations here:
 	pallet_nomination_pools::migration::v5::MigrateToV5<Runtime>,
 	parachains_configuration::migration::v5::MigrateToV5<Runtime>,
 );

runtime/polkadot/src/lib.rs

@@ -1412,14 +1412,15 @@ impl Get<Perbill> for NominationPoolsMigrationV4OldPallet {
 
 /// All migrations that will run on the next runtime upgrade.
 ///
-/// Should be cleared after every release.
+/// This contains the combined migrations of the last 10 releases. It allows to skip runtime upgrades in case governance decides to do so.
 #[allow(deprecated)]
 pub type Migrations = (
+	// 0.9.40
 	pallet_nomination_pools::migration::v4::MigrateToV4<
 		Runtime,
 		NominationPoolsMigrationV4OldPallet,
 	>,
-	// NOTE: If we don't propose 0.9.40 on chain; these two can be replaced with `MigrateV3ToV5`.
+	// Unreleased - add new migrations here:
 	pallet_nomination_pools::migration::v5::MigrateToV5<Runtime>,
 	parachains_configuration::migration::v5::MigrateToV5<Runtime>,
 );

runtime/rococo/src/lib.rs

@@ -1493,8 +1493,9 @@ pub type UncheckedExtrinsic =
 
 /// All migrations that will run on the next runtime upgrade.
 ///
-/// Should be cleared after every release.
-pub type Migrations = parachains_configuration::migration::v5::MigrateToV5<Runtime>;
+/// This contains the combined migrations of the last 10 releases. It allows to skip runtime
+/// upgrades in case governance decides to do so.
+pub type Migrations = (parachains_configuration::migration::v5::MigrateToV5<Runtime>);
 
 /// Executive: handles dispatch to the various modules.
 pub type Executive = frame_executive::Executive<

runtime/westend/src/lib.rs

@@ -1207,14 +1207,17 @@ impl Get<Perbill> for NominationPoolsMigrationV4OldPallet {
 
 /// All migrations that will run on the next runtime upgrade.
 ///
-/// Should be cleared after every release.
+/// This contains the combined migrations of the last 10 releases. It allows to skip runtime
+/// upgrades in case governance decides to do so.
 #[allow(deprecated)]
 pub type Migrations = (
+	// 0.9.40
 	clean_state_migration::CleanMigrate,
 	pallet_nomination_pools::migration::v4::MigrateToV4<
 		Runtime,
 		NominationPoolsMigrationV4OldPallet,
 	>,
+	// Unreleased - add new migrations here:
 	pallet_nomination_pools::migration::v5::MigrateToV5<Runtime>,
 	parachains_configuration::migration::v5::MigrateToV5<Runtime>,
 );