title: why is there the error "No plugin found for prefix 'help' in the current project" when I write mvn help:effective-pom in the command prompt?
body: <p>I'm reading a tutorial about maven and it should be mentioned that I know nothing about it. I have done first and second chapter successfully which was about it's setup. but in chapter 3 which is "Maven Pom" I have a problem. In last paragraph it says to make a "pom.xml" file in any directory you wish and write this in it:</p>
  
  <pre><code> &lt;project xmlns="http://maven.apache.org/POM/4.0.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
     http://maven.apache.org/xsd/maven-4.0.0.xsd"&gt;
     &lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
  
     &lt;groupId&gt;com.companyname.project-group&lt;/groupId&gt;
     &lt;artifactId&gt;project&lt;/artifactId&gt;
     &lt;version&gt;1.0&lt;/version&gt;
  
  &lt;/project&gt;
  </code></pre>
  
  <p>and then it says  that an easy way to look at the default configurations of the super POM is by running the following command: <code>mvn help:effective-pom</code> in the command prompt.</p>
  
  <p>But when I try this, I get this error:</p>
  
  <pre><code>No plugin found for prefix 'help' in the current project
  </code></pre>
  
  <p>This is the tutorial I mentioned above: <a href="http://www.tutorialspoint.com/maven/maven_quick_guide.htm" rel="noreferrer">maven tutorial</a></p>
  
  <p>Why there is no plugin help in my repository folder?! and how I can get it?</p>
  
  <p>This is the output of mvn --version in the cmd:</p>
  
  <pre><code>Apache Maven 3.2.3
  Maven home: C:\apache-maven-3.2.3
  Java version: 1.6.0_13
  Java home: C:\Program Files\Java\jdk1.6.0_13
  Default locale: en_US, platform encoding: Cp1252
  OS name: "windows Vista",version:"6.8"
  </code></pre>
  
  <p>This is the rezult of mvn -X help:effective-pom(first ten lines)</p>
  
  <pre><code>[INFO] Scanning for projects...
  Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.pom
  
  [WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-clean-plugin:2.5: Plugin org.apache.maven.plugins:maven-clean-plugin:2.5 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-clean-plugin:jar:2.5
  Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-install-plugin/2.4/maven-install-plugin-2.4.pom
  
  [WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-install-plugin:2.4: Plugin org.apache.maven.plugins:maven-install-plugin:2.4 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-install-plugin:jar:2.4
  Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-resources-plugin/2.6/maven-resources-plugin-2.6.pom
  
  [WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-resources-plugin:2.6: Plugin org.apache.maven.plugins:maven-resources-plugin:2.6 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-resources-plugin:jar:2.6
  Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-surefire-plugin/2.12.4/maven-surefire-plugin-2.12.4.pom
  
  [WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-surefire-plugin:2.12.4: Plugin org.apache.maven.plugins:maven-surefire-plugin:2.12.4 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-surefire-plugin:jar:2.12.4
  Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-compiler-plugin/3.1/maven-compiler-plugin-3.1.pom
  
  [WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-compiler-plugin:3.1: Plugin org.apache.maven.plugins:maven-compiler-plugin:3.1 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-compiler-plugin:jar:3.1
  Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-jar-plugin/2.4/maven-jar-plugin-2.4.pom
  
  [WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-jar-plugin:2.4: Plugin org.apache.maven.plugins:maven-jar-plugin:2.4 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-jar-plugin:jar:2.4
  Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-deploy-plugin/2.7/maven-deploy-plugin-2.7.pom
  
  [WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-deploy-plugin:2.7: Plugin org.apache.maven.plugins:maven-deploy-plugin:2.7 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-deploy-plugin:jar:2.7
  Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-site-plugin/3.3/maven-site-plugin-3.3.pom
  </code></pre>