[maven-release-plugin] prepare release r4.12

pom.xml

@@ -4,7 +4,7 @@
 
     <groupId>junit</groupId>
     <artifactId>junit</artifactId>
-    <version>4.12-SNAPSHOT</version>
+    <version>4.12</version>
 
     <name>JUnit</name>
     <description>JUnit is a unit testing framework for Java, created by Erich Gamma and Kent Beck.</description>
@@ -72,7 +72,7 @@
         <connection>scm:git:git://github.com/junit-team/junit.git</connection>
         <developerConnection>scm:git:[email protected]:junit-team/junit.git</developerConnection>
         <url>http://github.com/junit-team/junit/tree/master</url>
-      <tag>HEAD</tag>
+      <tag>r4.12</tag>
   </scm>
     <issueManagement>
         <system>github</system>