Initial version of bridging pallets as git subtree

.github/pr-custom-review.yml

@@ -19,12 +19,20 @@ rules:
     check_type: changed_files
     condition:
       include: .*
-      # excluding files from 'Runtime files' and 'CI files' rules
+      # excluding files from 'Runtime files' and 'CI files' rules and `Bridges subtree files`
       exclude: ^parachains/runtimes/assets/(statemine|statemint)/src/[^/]+\.rs$|^parachains/runtimes/bridge-hubs/(bridge-hub-kusama|bridge-hub-polkadot)/src/[^/]+\.rs$|^parachains/runtimes/collectives/collectives-polkadot/src/[^/]+\.rs$|^parachains/common/src/[^/]+\.rs$|^\.gitlab-ci\.yml|^scripts/ci/.*|^\.github/.*
     min_approvals: 2
     teams:
       - core-devs
 
+  # if there are any changes in the bridges subtree (in case of backport changes back to bridges repo)
+  - name: Bridges subtree files
+    check_type: changed_files
+    condition: ^bridges/.*
+    min_approvals: 1
+    teams:
+      - bridges-core
+
   - name: CI files
     check_type: changed_files
     condition:

BRIDGES.md

@@ -0,0 +1,88 @@
+# Using Parity Bridges Common dependency (`git subtree`).
+
+In `./bridges` sub-directory you can find a `git subtree` imported version of:
+[parity-bridges-common](https://github.com/paritytech/parity-bridges-common/) repository.
+
+(For regular Cumulus contributor 1. is relevant) \
+(For Cumulus maintainer 1. and 2. are relevant) \
+(For Bridges team 1. and 2. and 3. are relevant)
+
+# 1. How to fix broken Bridges code?
+
+To fix Bridges code simply create a commit in current (`Cumulus`) repo. Best if
+the commit is isolated to changes in `./bridges` sub-directory, because it makes
+it easier to import that change back to upstream repo.
+
+(Any changes to `bridges` subtree require Bridges team approve and they should manage backport to Bridges repo)
+
+
+# 2. How to pull latest Bridges code to the `bridges` subtree
+(in practice)
+```
+cd <cumulus-git-repo-dir>
+
+# this will update new git branches from bridges repo
+# there could be unresolved conflicts, but dont worry,
+# lots of them are caused because of removed unneeded files with patch step,
+./scripts/bridges_update_subtree.sh fetch
+
+# so, after fetch and before solving conflicts just run patch,
+# this will remove unneeded files and checks if subtree modules compiles
+./scripts/bridges_update_subtree.sh patch
+
+# if there are conflicts, this could help,
+# this removes locally deleted files at least (move changes to git stash for commit)
+./scripts/bridges_update_subtree.sh merge
+
+# (optional) when conflicts resolved, you can check build again - should pass
+# also important: this updates global Cargo.lock
+./scripts/bridges_update_subtree.sh patch
+
+# add changes to the commit, first command `fetch` starts merge,
+# so after all conflicts are solved and patch passes and compiles,
+# then we need to finish merge with:
+git merge --continue
+````
+
+# 3. How to pull latest Bridges code or contribute back?
+(in theory)
+
+Note that it's totally fine to ping the **Bridges Team** to do that for you. The point
+of adding the code as `git subtree` is to **reduce maintenance cost** for Cumulus/Polkadot
+developers.
+
+If you still would like to either update the code to match latest code from the repo
+or create an upstream PR read below. The following commands should be run in the
+current (`polkadot`) repo.
+
+1. Add Bridges repo as a local remote:
+```
+$ git remote add -f bridges git@github.com:paritytech/parity-bridges-common.git
+```
+
+If you plan to contribute back, consider forking the repository on Github and adding
+your personal fork as a remote as well.
+```
+$ git remote add -f my-bridges git@github.com:tomusdrw/parity-bridges-common.git
+```
+
+2. To update Bridges:
+```
+$ git fetch bridges master
+$ git subtree pull --prefix=bridges bridges master --squash
+````
+
+We use `--squash` to avoid adding individual commits and rather squashing them
+all into one.
+
+3. Clean unneeded files here:
+```
+./bridges/scripts/verify-pallets-build.sh --ignore-git-state --no-revert
+```
+
+4. Contributing back to Bridges (creating upstream PR)
+```
+$ git subtree push --prefix=bridges my-bridges master
+```
+This command will push changes to your personal fork of Bridges repo, from where
+you can simply create a PR to the main repo.