[SCM-895] Starteam tag command inverts logic of tagging subsets of directories

This closes #40
diff --git a/maven-scm-providers/maven-scm-provider-starteam/src/main/java/org/apache/maven/scm/provider/starteam/command/tag/StarteamTagCommand.java b/maven-scm-providers/maven-scm-provider-starteam/src/main/java/org/apache/maven/scm/provider/starteam/command/tag/StarteamTagCommand.java
index e95c182..4c0ba10 100644
--- a/maven-scm-providers/maven-scm-provider-starteam/src/main/java/org/apache/maven/scm/provider/starteam/command/tag/StarteamTagCommand.java
+++ b/maven-scm-providers/maven-scm-provider-starteam/src/main/java/org/apache/maven/scm/provider/starteam/command/tag/StarteamTagCommand.java
@@ -58,7 +58,7 @@
                                            ScmTagParameters scmTagParameters )
         throws ScmException
     {
-        if ( fileSet.getFileList().isEmpty() )
+        if ( !fileSet.getFileList().isEmpty() )
         {
             throw new ScmException( "This provider doesn't support tagging subsets of a directory" );
         }