update readme

README.md

@@ -11,3 +11,13 @@ How to use locally:
     git submodule update
     # make sure to use some parallel jobs
     pbuild --buildjobs=XXX --jobs=YYY --root=/space --buildtrigger=local --vm-memory=8192 --vm-disk-size=32768
+
+
+## local changes
+
+to apply local changes to specific packages
+- fork the package on gitea
+- git submodule set-url foo ../foo.git
+- cd foo; git checkout -b mine
+- fix fix fix
+- git push --set-upstream origin mine