Release Process

Principles and Benefits

• main should always be release-able
• a chain of commits in the release branch from main provide provenance of a release
• the ability to merge PRs into main is uninhibited by the release process, and the release process itself is not encumbered by changes to main
• the RC process provides a crisp delineation of burn-in build artifacts and final release artifacts
• cherry-picking commits to compose a release remains possible, if discouraged

Example Release Workflow for a hypothetical HL Besu 24.7.3

Burn-in candidate release steps (Day 0)

1. Create a PR against main to bump the build version to 24.7.4-SNAPSHOT and add a new version section to CHANGELOG.md to reflect the next snapshot revision
   1. This prevents blocking main during the release but creates a bookmark to indicate that the release will include up to the commit before this.
   2. This also prevents later releases colliding with release numbers used on a disposable, release branch.
2. Create a release candidate PR which merges `main` into the `release` branch, which also updates the build version to reflect 24.7.3-RC1
   1. During the actual 24.7.3 release, it became clear that the only way to do this nicely is by cherry-picking the commit range from main onto the release branch, e.g. git cherry-pick 6dc10a9..eef40bd 
   2. Due to 1, we need to use a subset of main commits, not including the bump to 24.7.4-SNAPSHOT
3. When release branch exists and is tagged, any pre-release activities may commence. This usually includes executing a long-running (about 48 hours) "burn in" process which deploys new nodes to sync from scratch on a variety of networks, using a variety of CL clients.
4. At this point, there is no published artifact, and testing may take as long as deemed necessary.

Final release steps (Day X)

Upon successful validation of the release candidate burn-in:

1. create a PR against the release branch to update ONLY the build version to 24.7.3, removing the -RC suffix
2. upon successful build and merge of the release PR:
   1. draft a new github release for 24.7.3
   2. publish the github release and announce on HL discord
   3. build artifacts will be attached to the release, and accurate SHAs and docker locations will be amended.
3. Trigger release process for documentation - Documentation release process
4. Homebrew release

Burn-in failures and hotfixes

An alternate outcome where the burn-in fails is a no-op.  Nothing needs to happen to 'cancel the release'.   We can either skip this release version (and note that outcome in CHANGELOG.md), or build an RC2 candidate by restarting the burn-in candidate steps at step #2 with the new RC number.  

This process leaves a cherry-pick escape hatch for hotfixes that is minimum friction for the latest release at least. The biggest element of friction here is the PR which merges main into the release would need to handle the merge conflict that a cherry-pick creates.  This implies that it would be desirable for cherry-picking should to be a rare event, that is done with care. 

Comments, feedback, and clarification are all welcome.