Merge pull request #146 from /issues/145-document-upstream

Fix #145: Document working with upstream

docs-private/GitHub.md

@@ -0,0 +1,22 @@
+# GitHub
+
+This project `enrollment-server-wultra` is a downstream project of `enrollment-server`.
+
+
+## Setup a remote repository
+
+```shell
+git remote add upstream [email protected]:wultra/enrollment-server.git
+```
+
+See [Configuring a remote repository for a fork](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/configuring-a-remote-repository-for-a-fork) for details.
+
+
+## Merge upstream
+
+```shell
+git checkout -b issues/merge-upstream
+git fetch upstream
+git merge upstream/develop
+git push -u origin issues/merge-upstream
+```