Add documentation for the addInstanceNameInSubject variable
Change-Id: Ic995390210ea42ab6226ccba579afec9821c2de5
diff --git a/Documentation/config-mail.txt b/Documentation/config-mail.txt
index 686dfb8..40a6284 100644
--- a/Documentation/config-mail.txt
+++ b/Documentation/config-mail.txt
@@ -229,6 +229,10 @@
+
The Gerrit instance name, followed by the short project name
+$addInstanceNameInSubject::
++
+Whether the instance name should be included in the email subject.
+
$sshHost::
+
SSH hostname for the Gerrit instance.