- leave /guides/upgrade as symlink

upgrade/v2012-Developer-Upgrade-Guide.md

+<!-- --- title: Developer Upgrade Guide (OpenFOAM-v2012) -->
+
+[![home](/icons/home.svg "wiki home")](/home)
+[![upgrade](/icons/chevrons-up.svg "upgrade guide")][upgrade-guide]
+[![code](/icons/code.svg "coding patterns")][code-patterns]
+
+***Preview information, subject to change at any time !!!***
+
+[[_TOC_]]
+
+## Deprecation and Removal
+
+### Deprecated Methods
+
+### Removed Methods
+
+### Removed Items
+
+## Changes in definition
+
+## Changes in behaviour
+
+## Namespace changes
+
+[code-patterns]: /coding/patterns/patterns
+
+[v2012-notes]: https://www.openfoam.com/releases/openfoam-v2012/