Create stable-4.15 branch

Author: fingolfin

Makefile.rules

@@ -1067,7 +1067,7 @@ testkernel: ${KERNELTESTS}
 ########################################################################
 
 # change PKG_BRANCH to stable-X.Y in the stable branch
-PKG_BRANCH = master
+PKG_BRANCH = stable-4.15
 PKG_BOOTSTRAP_URL = https://github.com/gap-system/PackageDistro/releases/download/latest/
 PKG_MINIMAL = packages-required.tar.gz
 PKG_FULL = packages.tar.gz

README.md

@@ -1,5 +1,5 @@
 [![Build Status](https://github.com/gap-system/gap/actions/workflows/CI.yml/badge.svg)](https://github.com/gap-system/gap/actions/workflows/CI.yml)
-[![Code Coverage](https://codecov.io/gh/gap-system/gap/branch/master/graphs/badge.svg)](https://codecov.io/gh/gap-system/gap/branch/master)
+[![Code Coverage](https://codecov.io/gh/gap-system/gap/branch/stable-4.15/graphs/badge.svg)](https://codecov.io/gh/gap-system/gap/branch/stable-4.15)
 [![ref](https://img.shields.io/badge/docs-ref-blue)](https://gap-system.github.io/gap/doc/ref/chap0_mj.html)
 [![dev](https://img.shields.io/badge/docs-dev-blue)](https://gap-system.github.io/gap/doc/dev/chap0_mj.html)
 [![hpc](https://img.shields.io/badge/docs-hpc-blue)](https://gap-system.github.io/gap/doc/hpc/chap0_mj.html)