Test against stable28 branches

Signed-off-by: Joas Schilling <coding@schilljs.com>

.github/workflows/performance.yml

             curl -s -u test:test -T README.md http://localhost:8080/remote.php/dav/files/test/new_file.txt
             curl -s -u test:test -X DELETE http://localhost:8080/remote.php/dav/files/test/new_file.txt
           output: before.json
-          profiler-branch: master
+          profiler-branch: stable28
 
       - name: Apply PR
         run: |
             curl -s -u test:test -T README.md http://localhost:8080/remote.php/dav/files/test/new_file.txt
             curl -s -u test:test -X DELETE http://localhost:8080/remote.php/dav/files/test/new_file.txt
           output: after.json
-          profiler-branch: master
+          profiler-branch: stable28
           compare-with: before.json
 
       - name: Upload profiles

README.md

 # Nextcloud Server ☁
-[![Scrutinizer Code Quality](https://scrutinizer-ci.com/g/nextcloud/server/badges/quality-score.png?b=master)](https://scrutinizer-ci.com/g/nextcloud/server/?branch=master)
-[![codecov](https://codecov.io/gh/nextcloud/server/branch/master/graph/badge.svg)](https://codecov.io/gh/nextcloud/server)
+[![Scrutinizer Code Quality](https://scrutinizer-ci.com/g/nextcloud/server/badges/quality-score.png?b=stable28)](https://scrutinizer-ci.com/g/nextcloud/server/?branch=master)
+[![codecov](https://codecov.io/gh/nextcloud/server/branch/stable28/graph/badge.svg)](https://codecov.io/gh/nextcloud/server)
 [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/209/badge)](https://bestpractices.coreinfrastructure.org/projects/209)
 [![Design](https://contribute.design/api/shield/nextcloud/server)](https://contribute.design/nextcloud/server)
 

build/update-apps.sh

 #!/bin/bash
-# Update Nextcloud apps from latest git master
+# Update Nextcloud apps from latest git stable28
 # For local development environment
 # Use from Nextcloud server folder with `./build/update-apps.sh`
 #
 # It automatically:
 # - goes through all apps which are not shipped via server
 # - shows the app name in bold and uses whitespace for separation
-# - changes to master and pulls quietly
+# - changes to stable28 and pulls quietly
 # - shows the 3 most recent commits for context
-# - removes branches merged into master
+# - removes branches merged into stable28
 # - … could even do the build steps if they are consistent for the apps (like `make`)
 
-find apps* -maxdepth 2 -name .git -exec sh -c 'cd {}/../ && printf "\n\033[1m${PWD##*/}\033[0m\n" && git checkout master && git pull --quiet -p && git --no-pager log -3 --pretty=format:"%h %Cblue%ar%x09%an %Creset%s" && printf "\n" && git branch --merged master | grep -v "master$" | xargs git branch -d && cd ..' \;
+find apps* -maxdepth 2 -name .git -exec sh -c 'cd {}/../ && printf "\n\033[1m${PWD##*/}\033[0m\n" && git checkout stable28 && git pull --quiet -p && git --no-pager log -3 --pretty=format:"%h %Cblue%ar%x09%an %Creset%s" && printf "\n" && git branch --merged stable28 | grep -v "stable28$" | xargs git branch -d && cd ..' \;

build/update.sh

 #!/bin/bash
-# Update Nextcloud server and apps from latest git master
+# Update Nextcloud server and apps from latest git stable28
 # For local development environment
 # Use from Nextcloud server folder with `./build/update.sh`
 
 # Update server
 printf "\n\033[1m${PWD##*/}\033[0m\n"
-git checkout master
+git checkout stable28
 git pull --quiet -p
 git --no-pager log -3 --pretty=format:"%h %Cblue%ar%x09%an %Creset%s"
 printf "\n"
-git branch --merged master | grep -v "master$" | xargs git branch -d
+git branch --merged stable28 | grep -v "stable28$" | xargs git branch -d
 git submodule update --init
 
 # Update apps

codecov.yml

 codecov:
-  branch: master
+  branch: stable28
   ci:
   - drone.nextcloud.com
   - '!scrutinizer-ci.com'