- leave /guides/upgrade as symlink

upgrade/v1712-User-Upgrade-Guide.md

+<!-- --- title: User Upgrade Guide (OpenFOAM-v1712) -->
+
+[![home](/icons/home.svg "wiki home")](/home)
+[![upgrade](/icons/chevrons-up.svg "upgrade guide")][upgrade-guide]
+[![code](/icons/code.svg "coding patterns")][code-patterns]
+
+[[_TOC_]]
+
+## Solver
+
+### chtMultiRegion solvers
+`system/fvSolution` file is now mandatory
+
+## Input dictionaries
+Special treatment for the dictionary `include` keyword has was removed after being deprecated many versions ago.
+
+## Utilities
+
+### applyBoundaryLayer
+Writing the turbulence viscosity field nut is now optional via the option -write-nut
+
+### noise
+Power of 2 data samples constraint was removed
+
+## Function objects
+`secondaryWrite` option in the `system/controlDict` superseded by the `writeObject` function object.
+
+
+[code-patterns]: /coding/patterns/patterns
+[upgrade-guide]: /upgrade/upgrade
+
+[v1712-notes]: https://www.openfoam.com/releases/openfoam-v1712/