Clarified branching and versioning for plugins. (#33)

* Clarified branching and versioning for plugins.

Signed-off-by: dblock <[email protected]>

* Clarified 3 branches.

Signed-off-by: dblock <[email protected]>

RELEASING.md

@@ -1,7 +1,9 @@
 - [Overview](#overview)
 - [Branching](#branching)
-  - [Release Branching](#release-branching)
-  - [Feature Branches](#feature-branches)
+    - [OpenSearch Branching](#opensearch-branching)
+    - [Plugin Branching](#plugin-branching)
+    - [Versioning](#versioning)
+    - [Feature Branches](#feature-branches)
 - [Release Labels](#release-labels)
 - [Releasing](#releasing)
 - [Backporting](#backporting)
@@ -12,16 +14,33 @@ This document explains the release strategy for artifacts in this organization.
 
 ## Branching
 
-### Release Branching
+Projects create a new branch when they need to start working on 2 separate versions of the product, with the `main` branch being the furthermost release. 
 
-Given the current major release of 1.0, projects in this organization maintain the following active branches.
+### OpenSearch Branching
 
-* **main**: The next _major_ release. This is the branch where all merges take place and code moves fast.
-* **1.x**: The next _minor_ release. Once a change is merged into `main`, decide whether to backport it to `1.x`.
-* **1.0**: The _current_ release. In between minor releases, only hotfixes (e.g. security) are backported to `1.0`.
+[OpenSearch](https://github.com/opensearch-project/OpenSearch) typically tracks 3 releases in parallel. For example, given the last major release of 1.0, OpenSearch in this organization maintains the following active branches.
+
+* **main**: The _next major_ release, currently 2.0. This is the branch where all merges take place, and code moves fast.
+* **1.x**: The _next minor_ release, currently 1.1. Once a change is merged into `main`, decide whether to backport it to `1.x`.
+* **1.0**: The _current_ release, currently 1.0. In between minor releases, only hotfixes (e.g. security) are backported to `1.0`. The next release out of this branch will be 1.0.1.
 
 Label PRs with the next major version label (e.g. `2.0.0`) and merge changes into `main`. Label PRs that you believe need to be backported as `1.x` and `1.0`. Backport PRs by checking out the versioned branch, cherry-pick changes and open a PR against each target backport branch.
 
+### Plugin Branching
+
+Plugins, such as [job-scheduler](https://github.com/opensearch-project/job-scheduler) aren't as active as OpenSearch, and typically track 2 releases in parallel instead of 3. This still translates into 3 branches. For example, given the last major release of 1.0, job-scheduler maintains the following.
+
+* **main**: The _next_ release, currently 1.1. This is the branch where all merges take place, and code moves fast.
+* **1.x**: A common parent branch for the series of 1.x releases. This is where 1.x patches will be made when `main` becomes 2.0.
+* **1.0**: The _current_ release, currently 1.0. This branch's parent is `1.x` to make future merges easier. 'In between minor releases, only hotfixes (e.g. security) are backported to `1.0`. The next release out of this branch will be 1.0.1.
+
+### Versioning
+
+Versions are incremented as soon as development starts on a given version to avoid confusion. In the examples above versions are as follows.
+
+* OpenSearch: `main` = 2.0, `1.x` = 1.1, and `1.0` = 1.0
+* job-scheduler: `main` = 1.1, `1.0` = 1.0
+
 ### Feature Branches
 
 Do not creating branches in the upstream repo, use your fork, for the exception of long lasting feature branches that require active collaboration from multiple developers. Name feature branches `feature/<thing>`. Once the work is merged to `main`, please make sure to delete the feature branch.