Explain 'Automatically resolve conflicts'

In the Gerrit documentation explain the project option 'Automatically
resolve conflicts'.

Change-Id: Ib43316092001d5f02ba68507c95c7bfd3ad049ce
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

Documentation/project-setup.txt

diff --git a/Documentation/project-setup.txt b/Documentation/project-setup.txt
index 9e4f556..1dca993 100644
--- a/Documentation/project-setup.txt
+++ b/Documentation/project-setup.txt
@@ -100,6 +100,11 @@
 the right order since inter-change dependencies will not be
 enforced for them.
 
+When Gerrit tries to do a merge, by default the merge will only
+succeed if there is no path conflict. By selecting the checkbox
+`Automatically resolve conflicts` Gerrit will try do a content merge
+if a path conflict occurs.
+
 
 Registering Additional Branches
 -------------------------------