Add README_HELM_CHART2_DEV.md and update README_AIRFLOW3_DEV.md

Author: bugraoz93

dev/README_AIRFLOW3_DEV.md

@@ -22,7 +22,8 @@
 
 - [Main branch is Airflow 3.x](#main-branch-is-airflow-3x)
 - [Contributors](#contributors)
-  - [Developing for Providers and the Helm Chart](#developing-for-providers-and-the-helm-chart)
+  - [Developing for the Helm Chart](#developing-for-the-helm-chart)
+  - [Developing for Providers](#developing-for-providers)
   - [Developing for Airflow 3.x, 3.1.x](#developing-for-airflow-3x-31x)
   - [Developing for Airflow 3](#developing-for-airflow-3)
   - [Developing for Airflow 2.11.x](#developing-for-airflow-211x)
@@ -49,7 +50,11 @@ Airflow 2.11.x releases will be cut from `v2-11-stable` branch.
 
 The following section explains which branches you should target with your PR.
 
-## Developing for Providers and the Helm Chart
+## Developing for the Helm Chart
+
+Please check the [README_HELM_CHART2_DEV.md](README_HELM_CHART2_DEV.md)
+
+## Developing for Providers
 
 PRs should target the `main` branch.
 Make sure your changes are only related to Providers or the Helm chart.

dev/README_HELM_CHART2_DEV.md

@@ -0,0 +1,133 @@
+<!--
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements.  See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership.  The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License.  You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing,
+ software distributed under the License is distributed on an
+ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ KIND, either express or implied.  See the License for the
+ specific language governing permissions and limitations
+ under the License.
+-->
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+**Table of contents**
+
+- [Main branch is Airflow Helm Chart 2.x](#main-branch-is-airflow-helm-chart-2x)
+- [Contributors](#contributors)
+  - [Why separate branches?](#why-separate-branches)
+  - [Developing for Airflow Helm Chart 2.x](#developing-for-airflow-helm-chart-2x)
+  - [Developing for Airflow Helm Chart 1.2x.x](#developing-for-airflow-helm-chart-12xx)
+- [Committers / PMCs](#committers--pmcs)
+  - [Merging PRs targeted for Airflow Helm Chart 2.X](#merging-prs-targeted-for-airflow-helm-chart-2x)
+  - [What do we backport to `chart/v1-2x-test` branch?](#what-do-we-backport-to-chartv1-2x-test-branch)
+  - [Merging PRs for Airflow Chart 1.2x.x](#merging-prs-for-airflow-chart-12xx)
+- [Milestones for PR](#milestones-for-pr)
+  - [Set Airflow Helm Chart 2.0.0](#set-airflow-helm-chart-200)
+  - [Set Airflow Helm Chart 1.2x.x](#set-airflow-helm-chart-12xx)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
+# Main branch is Airflow Helm Chart 2.x
+
+The `main` branch is for **cleanup, deprecations, and preparation** toward Airflow Helm Chart `2.x`.
+Airflow Helm Chart `2.x` releases will be cut from `main` branch.
+Airflow Helm Chart `1.2x.x` releases will be cut from [chart/v1-2x-test](https://github.com/apache/airflow/tree/chart/v1-2x-test)
+
+> [!NOTE]
+> We follow a staged approach: cleanup and refurbishment happens on `main` first.
+> Once validated, relevant changes are cherry-picked to `chart/v1-2x-test`.
+> This separates stability (test branch) from preparation for the next major release (main).
+> Each cleanup/deprecation task is tracked via individual tickets linked to the umbrella issue.
+
+# Contributors
+
+The following section explains which branches you should target with your PR.
+
+## Why separate branches?
+
+After `1.20.0` release, we will maintain two branches for Airflow Helm Chart.
+Airflow Helm Chart `1.2x.x` will be the staircase versions for Airflow Helm Chart `2.x` versions.
+
+There is ongoing Airflow Helm Refurbish work, which includes cleanup, deprecations, breaking changes, and restructuring to reduce technical debt before cutting the next major release.
+We want to be able to merge bug-fixes and documentation changes that are relevant to the latest release of Airflow Helm Chart 1.2x series without being blocked by the ongoing work on Airflow Helm Chart 2.x.
+At the same time, we want to be able to merge cleanup, deprecations, and preparation work for Airflow Helm Chart 2.x on `main` without being blocked by the need to backport them to Airflow Helm Chart 1.2x series.
+
+For the refurbish work, we have a separate project in Apache Confluence:
+
+[Airflow Helm Refurbish Project in Apache Confluence](https://cwiki.apache.org/confluence/display/AIRFLOW/Helm+Refurbish)
+
+## Developing for Airflow Helm Chart 2.x
+
+PRs should target `main` branch.
+
+## Developing for Airflow Helm Chart 1.2x.x
+
+PR should target `chart/v1-2x-test` branch.
+
+> [!IMPORTANT]
+> The `chart/v1-2x-test` branch is **strictly for maintenance, stability, and compatibility**.
+> No new features will be added here.
+>
+> We do not accept new features or non-trivial refactorings.
+> We only accept bug-fixes and documentation changes that are relevant to the latest release.
+> If you want to contribute new features or non-trivial refactorings, please target `main` branch.
+> We will cherry-pick it to `chart/v1-2x-test` branch if we decide that it is relevant to the latest release.
+> `1.2x.x` will be the latest release of Airflow Helm Chart 1.2x series.
+> We will not cut any new major release from `chart/v1-2x-test` branch.
+
+# Committers / PMCs
+
+The following sections explains the protocol for merging PRs.
+
+## Merging PRs targeted for Airflow Helm Chart 2.X
+
+PRs should target `main` branch.
+We will cherry-pick relevant changes to `chart/v1-2x-test` branch if we decide that they are relevant to the latest release.
+
+
+## What do we backport to `chart/v1-2x-test` branch?
+
+The `chart/v1-2x-test` branch is for development of Airflow Helm Chart `1.2x.x`.
+We will backport bug-fixes and documentation changes that are relevant to the latest release.
+We will not backport new features or non-trivial refactorings.
+
+* **Cleanup/Deprecations** cherry-pick according to version deprecation policy.
+  * Each minor version of Airflow Helm Chart will include some level of deprecation warnings.
+  * These warnings will mainly aim to be dropped at 2.0.0.
+  * If agreed cleanup/deprecation is relevant to the latest release, it should be cherry-picked to `chart/v1-2x-test` branch.
+* **Bug-fixes** cherry-pick only those relevant to the latest chart release and not difficult to apply.
+* **CI changes** cherry-pick most CI changes to keep the bugfix branch up-to-date and CI green.
+* **Documentation changes** cherry-pick only if relevant to the latest chart release and not about features only in `main`.
+* **Minor refactorings in active areas** do not cherry-pick.
+* **New features** do not cherry-pick.
+
+
+## Merging PRs for Airflow Chart 1.2x.x
+
+PRs should target `chart/v1-2x-test` branch.
+We will not merge new features or non-trivial refactorings.
+We will only merge bug-fixes and documentation changes that are relevant to the latest release.
+
+
+# Milestones for PR
+
+## Set Airflow Helm Chart 2.0.0
+
+Milestone will be added only to the original PR.
+
+* PR targeting `main` branch for cleanup, deprecations, preparation work, or non-trivial refactoring should be added to `Airflow Helm Chart 2.0.0` milestone.
+
+## Set Airflow Helm Chart 1.2x.x
+
+Milestone will be added only to the original PR.
+
+* PR targeting `v1-2x-test` branch should be added to relevant release accordingly `Airflow Helm Chart 1.2x.x` milestone.
+  * The version depends on the release cycle and the decision of the maintainers such as `1.20.0`, `1.21.0`, etc.