Document: how to make relayer releases (#2860)

* RELEASE.md

* updated running-relayer.md

RELEASE.md

@@ -0,0 +1,166 @@
+## How to Release a New Version of Relayer
+
+This document has the reverse order - the steps required to make a release
+come first and details come in the last sections.
+
+### Making a Release
+
+All releases are supposed to be done from the
+[`polkadot-staging` branch](https://github.com/paritytech/parity-bridges-common/tree/polkadot-staging).
+This branch is assumed to contain changes, that are reviewed and audited.
+
+To prepare a release:
+
+1. Make sure all required changes are merged to the
+  [`polkadot-staging` branch](https://github.com/paritytech/parity-bridges-common/tree/polkadot-staging);
+
+2. Select release version: go to the `Cargo.toml` of `substrate-relay` crate
+  ([here](https://github.com/paritytech/parity-bridges-common/blob/polkadot-staging/relays/bin-substrate/Cargo.toml#L3))
+  to look for the latest version. Then increment the minor or major version.
+
+    **NOTE**: we are not going to properly support [semver](https://semver.org)
+    for the relayer. When we simply bump a chain versions or introduce small fixes,
+    minor version must be incremented. If changes are substantial (e.g. when
+    we'll release relayer for [bridges v2](https://github.com/paritytech/parity-bridges-common/milestone/17))
+    it'll make sense to increment major version;
+
+3. Open a PR with a `substrate-relay` version change (see previous point).
+  It could be combined with the (1) if changes are not large. Make sure to
+  add the [`A-release`](https://github.com/paritytech/parity-bridges-common/labels/A-release)
+  label to your PR - in the future we'll add workflow to make pre-releases
+  when such PR is merged to the `polkadot-staging` branch;
+
+4. Wait for approvals and merge PR, mentioned in (3);
+
+5. Checkout updated `polkadot-staging` branch and do `git pull`;
+
+6. Make a new git tag with the `substrate-relay` version:
+```sh
+git tag -a v1.5.0 -m "Release v1.5.0"
+git push origin v1.5.0
+```
+
+7. Pushing that tag triggers a new pipeline at
+  [GitLab](https://gitlab.parity.io/parity/mirrors/parity-bridges-common/-/pipelines).
+  Wait until until that pipeline succeeds. Make sure relayer docker image is published
+  to the [docker hub](https://hub.docker.com/r/paritytech/substrate-relay/tags);
+
+8. Go to the [`New Release`](https://github.com/paritytech/parity-bridges-common/releases/new)
+  section of the repository. Make sure to:
+
+  - set release name to "Release vX.Y.Z" (example: "Release v1.5.0");
+
+  - at the beginning of the Release Description add the important notes if needed;
+
+  - right below that, add the reference to the relayer docker image:
+```
+Docker reference: paritytech/substrate-relay:v1.5.0
+```
+
+  - (**IMPORTANT**) prepare the list of bundled chain versions and add it right after the
+    docker reference. Example:
+```
+Bundled Chain Versions:
+
+- Rococo: `1_003_000`;
+
+- Westend: `1_003_000`;
+
+- Kusama: `9410`;
+
+- Polkadot: `9410`;
+
+- Rococo Bridge Hub: `9410`;
+
+- Westend Bridge Hub: `9410`;
+
+- Kusama Bridge Hub: `9410`;
+
+- Polkadot Bridge Hub: `9410`;
+
+- Rococo Bulletin: `None` (must be specified in CLI);
+
+- Polkadot Bulletin: `None` (must be specified in CLI).
+```
+
+  - choose new and previous tags and hit the "Generate Release Notes" button;
+
+  - hit the "Publish Release" button.
+
+### When to Make a New Release
+
+The relayer from this repository supports multiple bridges:
+
+- `Rococo Bridge Hub` (aka `RBH`) <> `Westend Bridge Hub` (aka `WBH`) bridge;
+
+- `Rococo Bridge Hub` <> `Rococo Bulletin Chain` (aka `RBC`) bridge;
+
+- `Kusama Bridge Hub` (aka `KBH`) <> `Polkadot Bridge Hub` (aka `PBH`) bridge;
+
+- `Polkadot Bridge Hub` <> `Polkadot Bulletin Chain` (aka `PBC`) bridge.
+
+We run every relayer in two modes: one is to relay messages and associated finality
+proofs (it is usually `relay-headers-and-messages` subcommand) and the other is
+the equivocation detection relayer (`detect-equivocations` command). The relayer
+working in the former mode, submits transactions only to the chains it directly connects.
+Relayer, running in the latter mode, submits transactions to relay chains (e.g. to
+`Polkadot` or to `Kusama`).
+
+To submit transaction to some chain, relayer would need to know how to construct and
+properly encode this transaction. In current implementation, this information is
+hardcoded in the relayer code. This information may change from release to release,
+so we need to make a new relayer release once one of changes is upgraded.
+
+However, we are cheating here - for test bridges (`RBH` <> `WBH` and `RBH` <> `RBC`)
+we are running relayer in a mode, when it just uses this hardcoded information,
+ignoring actual runtime version. So normally we'll made releases only when following
+chain runtimes are changes: `Polkadot`, `Kusama`, `PBH`, `KBH`.
+
+### Adding Support for Updated Chain
+
+When one of involved chains is upgraded, we need to update the relayer code to
+support it. Normally it means:
+
+1. Bumping bundled chain versions in following places:
+
+- for `Rococo` and `RBH`: [here](https://github.com/paritytech/parity-bridges-common/blob/polkadot-staging/relays/bin-substrate/src/chains/rococo.rs);
+
+- for `Westend` and `WBH`: [here](https://github.com/paritytech/parity-bridges-common/blob/polkadot-staging/relays/bin-substrate/src/chains/westend.rs);
+
+- for `Kusama` and `KBH`: [here](https://github.com/paritytech/parity-bridges-common/blob/polkadot-staging/relays/bin-substrate/src/chains/polkadot.rs)
+
+- for `Polkadot` and `PBH`: [here](https://github.com/paritytech/parity-bridges-common/blob/polkadot-staging/relays/bin-substrate/src/chains/polkadot.rs);
+
+- for `PBC`: [here](https://github.com/paritytech/parity-bridges-common/blob/polkadot-staging/relays/bin-substrate/src/chains/polkadot_bulletin.rs).
+
+2. Regenerating bundled runtime wrapper code using `runtime-codegen` binary:
+
+If you can start updated chain node, it could be done using following command
+(assuming you're in the root of the repository):
+```sh
+cd tools/runtime-codegen
+cargo run --bin runtime-codegen -- --from-node-url "wss://rococo-rpc.polkadot.io:443" > ../../relays/client-rococo/src/codegen_runtime.rs
+```
+
+Otherwise, you'll need a runtime file. You may download it from:
+
+- [releases page](https://github.com/paritytech/polkadot-sdk/releases) of `polkadot-sdk`
+  for `Rococo`, `Westend`, `RBH` and `WBH`;
+
+- [releases page](https://github.com/polkadot-fellows/runtimes/releases) of `runtimes`
+  for `Kusama`, `Polkadot`, `KBH` and `PBH`.
+
+Then use the following command:
+```sh
+cd tools/runtime-codegen
+cargo run --bin runtime-codegen -- --from-wasm-file rococo_runtime.compact.compressed.wasm > ../../relays/client-rococo/src/codegen_runtime.rs
+```
+
+**IMPORTANT**: due to [well-known issue](https://github.com/paritytech/parity-bridges-common/issues/2669)
+with runtime codegen, you'll get compilation errors after updating.
+To fix it, execute following commands:
+```sh
+cargo +nightly fmt --all
+find . -name codegen_runtime.rs -exec \
+    sed -i 's/::sp_runtime::generic::Header<::core::primitive::u32>/::sp_runtime::generic::Header<::core::primitive::u32, ::sp_runtime::traits::BlakeTwo256>/g' {} +
+```

docs/running-relayer.md

@@ -247,15 +247,14 @@ need to set value of the `bridgedChainId` to `bhks`.
 
 ### Starting your Rococo <> Westend Relayer
 
-We are using the following docker image to run our own Rococo <> Westend relayer:
-
-[paritytech/bridges-common-relay:v2024-02-16-rococo-westend-relayer](https://hub.docker.com/layers/paritytech/bridges-common-relay/v2024-02-16-rococo-westend-relayer/images/sha256-5ba4260d6bc2ac9e97c2e05d875f6dc44ee9265011311f268b66b8a5a672ada3?context=explore)
-
-You can grab the sources and build it manually:
-
-[v2024-02-16-rococo-westend-relayer](https://github.com/paritytech/parity-bridges-common/releases/tag/v2024-02-16-rococo-westend-relayer)
-
-Once you have the docker, update variables and run the following script:
+You may find the relayer image reference in the
+[Releases](https://github.com/paritytech/parity-bridges-common/releases)
+of this repository. Make sure to check supported (bundled) versions
+of release there. For Rococo <> Westend bridge, normally you may use the
+latest published release. The release notes always contain the docker
+image reference and source files, required to build relayer manually.
+
+Once you have the docker image, update variables and run the following script:
 ```sh
 export DOCKER_IMAGE=<image-of-substrate-relay>