Merge pull request #149 from jadu/upgrade-notes

Added upgrade notes

UPGRADE-4.0.md

@@ -0,0 +1,34 @@
+# Upgrade from 3.x to 4.0
+
+## Migration update
+
+4.0 introduces a newer version of Doctrine which includes a change to the namespacing of the AbstractMigration class.
+
+If you have any migrations in your project that reference this class, the namespace reference will need to be updated.
+
+Change from:
+
+
+```
+Doctrine\DBAL\Migrations\AbstractMigration
+```
+
+to:
+
+```
+Doctrine\Migrations\AbstractMigration
+```
+
+The method signatures for many methods within this class have also changed. Migrations extending this abstract will therefore also need to be updated, for example changing from:
+
+```
+public function up(Schema $schema)
+```
+
+to:
+
+```
+public function up(Schema $schema): void
+```
+
+[A script is available to apply these changes to all migrations within a project.](https://gist.github.com/DenisYaschuk/d3ade2d88d058cf9c971cf9d1f580a0f)