Create README.md

Author: eranshapira

README.md

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+# Branch versions(Part 1)
+
+This article introduces a software development paradigm, which has been implemented and used on Verizon Media Group's Video syndication teams for the past 3 years.
+
+The 'Branch versions' concept allows stakeholders to test and verify different code variants without affecting production.
+
+On our teams, every code change, creates a branch version which allows product managers, QA teams and different customers to test and verify changes, without merging it to master.
+
+The impact is huge, just consider some of the following scenarios:
+
+1. A product manager has a preliminary idea, but to assess its value and refine requirements, more data is required.
+Serving a branch version to a group of users with a POC can contribute ideas for a better design and better product planning.
+
+2. A bug is reported - use branch versions to inspect, and before deploying the fix, assign the branch version to a user/PM/QA to verify the fix.
+Only then, you update your tests, submit a PR and merge to master.
+
+3. Easy rollback - A critical bug was deployed, requiring a fast rollback. Now, thanks to branch versions, we're storing every version created by every branch, including master branch, which allows you to easily transition all of your users to a specific version in a matter of seconds.
+
+(TBH - Scenario 3 never happened. avg. 90% unit tests coverage and branch versions)
+
+So, what defines a branch version?
+
+1. Isolation - The modified code is not part of master branch.
+2. Debug - Branch versions contain sourcemaps, debug info developers can inspect the code on multiple environments(extremely useful for cross-browser issues)
+3. Protected - A branch version can be used only by specific people. (recommended)
+
+The core concept is that a branch version simply represents a different deployment path.
+
+Let's dig deeper and see what it means...
+
+Webpack
+
+Let's examine [this simple React application](https://github.com/eranshapira/webpack-branch-versions).
+
+The key concepts we use in webpack are the following features:
+
+1. [dynamic imports](https://webpack.js.org/guides/code-splitting/#dynamic-imports) - each webpack entry point dynamically imports the rest of the bundle. ([js](https://github.com/eranshapira/webpack-branch-versions/blob/master/src/index.js) dynamically loads [js](https://github.com/eranshapira/webpack-branch-versions/blob/master/src/app.js))
+2. [output.publicPath](https://webpack.js.org/configuration/output/#outputpublicpath) - define an absolute path for bundles, which instructs webpack to load any asset without any relative path issues.
+
+CI/CD
+
+There is only one concept that we need to maintain in our CI/CD process - Deployment must be performed to the same path specified in webpack's config.output.publicPath.
+
+Server endpoint
+
+Now that we have an infrastructure to deploy different branch versions, we need to provide a way to use these versions.
+
+Examine [this very-basic-never-to-be-used server](https://github.com/eranshapira/webpack-branch-versions/blob/master/server/index.js), In our code, the html served in the response is changing the folder from which it loads main.js.