diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
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+# Contributing
+
+When contributing to this repository, please first discuss the change you wish to make via issue,
+email, or any other method with the owners of this repository before making a change. 
+
+Please see https://github.com/zokradonh/kopano-docker/blob/master/README.md#when-building-my-own-containers-how-can-i-make-sure-my-build-works-as-expected for testing remakrs
+
+Speeding up testing rebuilds:
+- `make vcs_ref=invalid build-web`