Clarify general override policy for config parameters Especially point out that config parameters that have a list of values are always completely overridden and it's not possible to just add a value to an inherited list. Signed-off-by: Edwin Kempin <ekempin@google.com> Change-Id: I52a909320bd71f176e38f76b3536bfb827b9252e

diff --git a/resources/Documentation/config.md b/resources/Documentation/config.md
index 6635c55..705c5de 100644
--- a/resources/Documentation/config.md
+++ b/resources/Documentation/config.md

@@ -11,7 +11,17 @@
 `@PLUGIN@.config` files that are stored in the `refs/meta/config` branches of
 the projects.
 
-Parameters that are not set for a project are inherited from the parent project.
+Parameters that are not set for a project are inherited from the parent project
+or the global configuration in `gerrit.config`.
+
+A config setting on project level overrides the corresponsing setting that is
+inherited from parent projects and the global configuration in `gerrit.config`.
+
+**NOTE:** Some configuration parameters have a list of values and can be
+specified multiple times (e.g. `disabledBranch`). If such a value is set on
+project level it means that the complete inherited list is overridden. It's
+*not* possible to just add a value to the inherited list, but if this is wanted
+the complete list with the additional value has to be set on project level.
 
 # <a id="globalConfiguration">Global configuration in gerrit.config</a>