[MNG-6078] Can't overwrite properties which have been defined in

.mvn/maven.config
 o Reversed the order of properties only to get the properties from
   command line at the end of the properties list which results
   in correct behaviour to be able to overwrite properties from
   command line for properties which have been defined in
   .mvn/maven.config file.

maven-embedder/src/main/java/org/apache/maven/cli/MavenCli.java

@@ -27,6 +27,7 @@
 import org.apache.commons.cli.CommandLine;
 import org.apache.commons.cli.ParseException;
 import org.apache.commons.cli.UnrecognizedOptionException;
+import org.apache.commons.lang3.ArrayUtils;
 import org.apache.maven.BuildAbort;
 import org.apache.maven.InternalErrorException;
 import org.apache.maven.Maven;
@@ -542,7 +543,9 @@ else if ( MavenExecutionRequest.CHECKSUM_POLICY_FAIL.equals( cliRequest.request.
         }
     }
 
-    private void properties( CliRequest cliRequest )
+    //Needed to make this method package visible to make writing a unit test possible
+    //Maybe it's better to move some of those methods to separate class (SoC).
+    void properties( CliRequest cliRequest )
     {
         populateProperties( cliRequest.commandLine, cliRequest.systemProperties, cliRequest.userProperties );
     }
@@ -1581,9 +1584,14 @@ static void populateProperties( CommandLine commandLine, Properties systemProper
         if ( commandLine.hasOption( CLIManager.SET_SYSTEM_PROPERTY ) )
         {
             String[] defStrs = commandLine.getOptionValues( CLIManager.SET_SYSTEM_PROPERTY );
-
+            
             if ( defStrs != null )
             {
+                //The following is needed to get precedence
+                //of properties which are defined on command line
+                //over properties defined in the .mvn/maven.config. 
+                ArrayUtils.reverse( defStrs );
+                
                 for ( String defStr : defStrs )
                 {
                     setCliProperty( defStr, userProperties );

maven-embedder/src/test/java/org/apache/maven/cli/MavenCliTest.java

@@ -21,10 +21,10 @@
 
 import java.io.File;
 
-import junit.framework.TestCase;
-
 import org.apache.commons.cli.ParseException;
 
+import junit.framework.TestCase;
+
 public class MavenCliTest
     extends TestCase
 {
@@ -81,8 +81,8 @@ public void testMavenConfig()
         // read .mvn/maven.config
         cli.initialize( request );
         cli.cli( request );
-        assertEquals( "multithreaded", request.commandLine.getOptionValue( "builder" ) );
-        assertEquals( "8", request.commandLine.getOptionValue( "threads" ) );
+        assertEquals( "multithreaded", request.commandLine.getOptionValue( CLIManager.BUILDER ) );
+        assertEquals( "8", request.commandLine.getOptionValue( CLIManager.THREADS ) );
 
         // override from command line
         request = new CliRequest( new String[] { "--builder", "foobar" }, null );
@@ -107,4 +107,49 @@ public void testMavenConfigInvalid()
 
         }
     }
+    
+    /**
+     * Read .mvn/maven.config with the following definitions:
+     * <pre>
+     *   -T 3
+     *   -Drevision=1.3.0
+     * </pre>
+     * and check if the {@code -T 3} option can be overwritten via command line
+     * argument.
+     * @throws Exception in case of failure.
+     */
+    public void testMVNConfigurationThreadCanBeOverwrittenViaCommandLine() throws Exception {
+        System.setProperty( MavenCli.MULTIMODULE_PROJECT_DIRECTORY, new File( "src/test/projects/mavenConfigProperties" ).getCanonicalPath() );
+        CliRequest request = new CliRequest( new String[]{ "-T", "5" }, null );
+
+        cli.initialize( request );
+        // read .mvn/maven.config
+        cli.cli( request );
+        
+        assertEquals( "5", request.commandLine.getOptionValue( CLIManager.THREADS ) );
+    }
+    
+    /**
+     * Read .mvn/maven.config with the following definitions:
+     * <pre>
+     *   -T 3
+     *   -Drevision=1.3.0
+     * </pre>
+     * and check if the {@code -Drevision-1.3.0} option can be overwritten via command line
+     * argument.
+     * @throws Exception
+     */
+    public void testMVNConfigurationDefinedPropertiesCanBeOverwrittenViaCommandLine() throws Exception {
+        System.setProperty( MavenCli.MULTIMODULE_PROJECT_DIRECTORY, new File( "src/test/projects/mavenConfigProperties" ).getCanonicalPath() );
+        CliRequest request = new CliRequest( new String[]{ "-Drevision=8.1.0"}, null );
+
+        cli.initialize( request );
+        // read .mvn/maven.config
+        cli.cli( request );
+        cli.properties( request );
+        
+        String revision = System.getProperty( "revision" );
+        assertEquals( "8.1.0", revision );
+
+    }
 }

maven-embedder/src/test/projects/mavenConfigProperties/.mvn/maven.config

@@ -0,0 +1,3 @@
+-T 3
+-Drevision=1.3.0
+