Add migration guide to alpha.20

docs/3.x.x/migration-guide/README.md

@@ -25,3 +25,4 @@
 - [Migration guide from alpha.16 to alpha.17](migration-guide-alpha.16-to-alpha.17.md)
 - [Migration guide from alpha.17 to alpha.18](migration-guide-alpha.17-to-alpha.18.md)
 - [Migration guide from alpha.18 to alpha.19](migration-guide-alpha.18-to-alpha.19.md)
+- [Migration guide from alpha.19 to alpha.20](migration-guide-alpha.19-to-alpha.20.md)

docs/3.x.x/migration-guide/migration-guide-alpha.19-to-alpha.20.md

@@ -0,0 +1,67 @@
+# Migration guide from alpha.19 to alpha.20
+
+**Here are the major changes:**
+
+- Fix email issue on user update
+- Improve GraphQL performances
+
+**Useful links:**
+- Changelog: [https://github.com/strapi/strapi/releases/tag/v3.0.0-alpha.20](https://github.com/strapi/strapi/releases/tag/v3.0.0-alpha.20)
+- GitHub diff: [https://github.com/strapi/strapi/compare/v3.0.0-alpha.19...v3.0.0-alpha.20](https://github.com/strapi/strapi/compare/v3.0.0-alpha.19...v3.0.0-alpha.20)
+
+<br>
+
+::: note
+Feel free to [join us on Slack](http://slack.strapi.io) and ask questions about the migration process.
+:::
+
+<br>
+
+## Getting started
+
+Install Strapi `alpha.20` globally on your computer. To do so run `npm install strapi@3.0.0-alpha.20 -g`.
+
+When it's done, generate a new empty project `strapi new myNewProject` (don't pay attention to the database configuration).
+
+<br>
+
+## Update node modules
+
+Update the Strapi's dependencies version (move Strapi's dependencies to `3.0.0-alpha.20` version) of your project.
+
+Run `npm install strapi@3.0.0-alpha.20 --save` to update your strapi version.
+
+<br>
+
+## Update the Admin
+
+::: note
+If you performed updates in the Admin, you will have to manually migrate your changes.
+:::
+
+Delete your old admin folder and replace it with the new one.
+
+<br>
+
+## Update the Plugins
+
+::: note
+If you did a custom update on one of the plugins, you will have to manually migrate your update.
+:::
+
+Copy the fields and relations you had in your `/plugins/users-permissions/models/User.settings.json` and `/plugins/users-permissions/config/jwt.json` file in the new one.
+
+Then, delete your old `plugins` folder and replace it with the new one.
+
+## Update services
+
+For both bookshelf and mongoose, you will have to update all services of your generated API.
+
+You will have to update one line of the `fetchAll` function.
+
+**Mongoose** replace `.populate(populate);` by `.populate(filters.populate || populate);`.
+**Bookshelf**: replace `withRelated: populate` by `withRelated: filters.populate || populate`.
+
+<br>
+
+That's all, you have now upgraded to Strapi `alpha.20`.