docs: explain versioning policy 1.x, 2.x, and beyond

docs/README.md

@@ -19,7 +19,7 @@ an issue:
 * [Glossary of Terms](glossary.md)
 * [Supported Platforms](tutorial/supported-platforms.md)
 * [Security](tutorial/security.md)
-* [Electron Versioning](tutorial/electron-versioning.md)
+* [Versioning](versioning.md)
 * [Application Distribution](tutorial/application-distribution.md)
 * [Mac App Store Submission Guide](tutorial/mac-app-store-submission-guide.md)
 * [Windows Store Guide](tutorial/windows-store-guide.md)

docs/development/releasing.md

@@ -11,7 +11,7 @@ This document describes the process for releasing a new version of Electron.
 Run `npm run prepare-release -- --notesOnly` to view auto generated release
 notes.  The notes generated should help you determine if this is a major, minor,
 patch, or beta version change. Read the
-[Version Change Rules](../tutorial/electron-versioning.md#version-change-rules) for more information.
+[Version Change Rules](../versioning.md#semver) for more information.
 
 ## Run the prepare-release script
 The prepare release script will do the following:
@@ -206,7 +206,7 @@ release to npm.
 
 [the releases page]: https://github.com/electron/electron/releases
 [this bump commit]: https://github.com/electron/electron/commit/78ec1b8f89b3886b856377a1756a51617bc33f5a
-[electron-versioning]: /docs/tutorial/electron-versioning.md
+[versioning]: /docs/versioning.md
 
 ## Fix missing binaries of a release manually
 

docs/tutorial/installation.md

@@ -11,7 +11,7 @@ npm install electron --save-dev
 ```
 
 See the 
-[Electron versioning doc](https://electronjs.org/docs/tutorial/electron-versioning)
+[Electron versioning doc](https://electron.atom.io/docs/versioning/)
 for info on how to manage Electron versions in your apps.
 
 ## Global Installation

docs/versioning.md

@@ -0,0 +1,136 @@
+# Electron Versioning
+
+## Version 1.x
+
+Electron versions *< 2.0* have not conformed to the [semver](http://semver.org) spec. Major versions corresponded to end-user API changes. Minor versions corresponded to Chromium major releases. Patch versions corresponded to new features and bug fixes. While convenient for developers merging features, it creates problems for developers of client-facing applications. The QA testing cycles of major apps like Slack, Stride, Teams, Skype, VS Code, Atom, and Desktop can be lengthy and stability is a highly desired outcome. There is a high risk in adopting new features while trying to absorb bug fixes.
+
+Here is an example of the 1.x strategy:
+
+![](versioning/sketch-0.png)
+
+An app developed with `1.8.1` cannot take the `1.8.3` bug fix without either absorbing the `1.8.2` feature, or by backporting the fix and maintaining a new release line.
+
+## Version 2.0 and Beyond
+
+There are several major changes from our 1.x strategy outlined below. Each change is intended to satisfy the needs and priorities of developers/maintainers and app developers.
+
+1. Strict use of semver
+2. Introduction of semver-compliant `-beta` tags
+3. Introduction of [semantic-release](https://github.com/semantic-release/semantic-release#default-commit-message-format) style commit messages
+4. Clearly defined stabilization branches
+5. Regular release cadence
+
+We will cover in detail how git branching works, how npm tagging works, what developers should expect to see, and how one can backport changes.
+
+# semver
+
+From 2.0 onward, Electron will follow semver.
+
+Below is a table explicitly mapping types of changes to their corresponding category of semver (e.g. Major, Minor, Patch).
+
+* **Major Version Increments**
+	* Chromium version updates
+	* node.js major version updates
+	* Electron breaking API changes
+* **Minor Version Increments**
+	* node.js  minor version updates
+	* Electron non-breaking API changes
+* **Patch Version Increments**
+	* node.js patch version updates
+	* fix-related chromium patches
+	* electron bug fixes
+
+Note that most chromium updates will be considered breaking. Fixes that can be backported will likely be cherry-picked as patches.
+
+# Stabilization Branches
+
+Stabilization branches are branches that run parallel to master, taking in only cherry-picked commits that are related to security or stability. These branches are never merged back to master.
+
+![](versioning/sketch-1.png)
+
+Stabilization branches are always either **major** or **minor** version lines, and named against the following template `$MAJOR-$MINOR-x` e.g. `2-0-x`.
+
+We allow for multiple stabilization branches to exist simultaneously, and intend to support at least two in parallel at all times, backporting security fixes as necessary.
+![](versioning/sketch-2.png)
+
+Older lines will not be supported by GitHub, but other groups can take ownership and backport stability and security fixes on their own. We discourage this, but recognize that it makes life easier for many app developers.
+
+# Beta Releases and Bug Fixes
+
+Developers want to know which releases are _safe_ to use. Even seemingly innocent features can introduce regressions in complex applications.  At the same time, locking to a fixed version is dangerous because you’re ignoring security patches and bug fixes that may have come out since your version. Our goal is to allow the following standard semver ranges in `package.json` :
+
+* Use `~2.0.0` to  admit only stability or security related fixes to your `2.0.0` release.
+* Use `^2.0.0` to admit non-breaking _reasonably stable_ feature work as well as security and bug fixes.
+
+What’s important about the second point is that apps using `^` should still be able to expect a reasonable level of stability. To accomplish this, semver allows for a _pre-release identifier_ to indicate a particular version is not yet _safe_ or _stable_.
+
+Whatever you choose, you will periodically have to bump the version in your `package.json` as breaking changes are a fact of Chromium life.
+
+The process is as follows:
+
+1. All new major and minor releases lines begin with a `-beta.N` tag for `N >= 1`. At that point, the feature set is **locked**. That release line admits no further features, and focuses only on security and stability.
+e.g. `2.0.0-beta.1`.
+2. Bug fixes, regression fixes, and security patches can be admitted. Upon doing so, a new beta is released incrementing `N`.
+e.g. `2.0.0-beta.2`
+3. If a particular beta release is _generally regarded_ as stable, it will be re-released as a stable build, changing only the version information.
+e.g. `2.0.0`.
+4. If future bug fixes or security patches need to be made once a release is stable, they are applied and the _patch_ version is incremented accordingly
+e.g. `2.0.1`.
+
+For each major and minor bump, you should expect too see something like the following:
+
+```
+2.0.0-beta.1
+2.0.0-beta.2
+2.0.0-beta.3
+2.0.0
+2.0.1
+2.0.2
+```
+
+An example lifecycle in pictures:
+
+* A new release branch is created that includes the latest set of features. It is published as  `2.0.0-beta.1`.
+![](versioning/sketch-3.png)
+* A bug fix comes into master that can be pack-ported to the release branch. The patch is applied, and a new beta is published as `2.0.0-beta.2`.
+![](versioning/sketch-4.png)
+* The beta is considered _generally stable_ and it is published again as a non-beta under `2.0.0`.
+![](versioning/sketch-5.png)
+* Later, a zero-day exploit is revealed and a fix is applied to master. We pack-port the fix to the `2-0-x` line and release `2.0.1`.
+![](versioning/sketch-6.png)
+
+A few examples of how various semver ranges will pick up new releases:
+
+![](versioning/sketch-7.png)
+
+# Missing Features: Alphas, and Nightly
+Our strategy has a few tradeoffs, which for now we feel are appropriate. Most importantly that new features in master may take a while before reaching a stable release line. If you want to try a new feature immediately, you will have to build Electron yourself.
+
+As a future consideration, we may introduce one or both of the following:
+
+* nightly builds off of master; these would allow folks to test new features quickly and give feedback
+* alpha releases that have looser stability constraints to betas; for example it would be allowable to admit new features while a stability channel is in _alpha_
+
+# Feature Flags
+Feature flags are a common practice in Chromium, and is well-established in the web-development ecosystem. In the context of Electron, a feature flag or **soft-branch** must have the following properties:
+
+* is is enabled/disabled either at runtime, or build-time; we do not support the concept of a request-scoped feature-flag
+* it completely segments new and old code paths; refactoring old code to support a new feature _violates_ the feature-flag contract
+* feature flags are eventually removed after the soft-branch is merged
+
+We reconcile flagged code with our versioning strategy as follows:
+
+1. we do not consider iterating on feature-flagged code in a stability branch; even judicious use of feature-flags is not without risk
+2. you may break API contracts in feature-flagged code without bumping the major version. Flagged code does not adhere to semver
+
+# Semantic Commits
+We seek to increase clarity at all levels of the update and releases process. Starting with `2.0.0` we will require that all commits adhere to the following commit-message standard _before_ merging to `master`.
+
+* Commits that would result in a semver **major** bump must start with `BREAKING CHANGE:`.
+* Commits that would result in a semver **minor** bump must start with `feat:`.
+* Commits that would result in a semver **patch** bump must start with `fix:`.
+
+All other commit messages will be rejected from merging to `master`.
+
+* We allow squashing of commits, provided that the squashed message adheres the the above message format.
+* A pull-request can contain non-conforming commit messages, however the commits must adhere to the naming standard _before_ a merge can be approved.