add tag element in scm to be able to release

Signed-off-by: Olivier Lamy <olamy@apache.org>

pom.xml

@@ -56,6 +56,7 @@
   <scm>
     <connection>scm:git:https://github.com/mojohaus/jdepend-maven-plugin.git</connection>
     <developerConnection>scm:git:ssh://git@github.com/mojohaus/jdepend-maven-plugin.git</developerConnection>
+    <tag>HEAD</tag>
     <url>https://github.com/mojohaus/jdepend-maven-plugin</url>
   </scm>
   <issueManagement>