title: Git plugin for Hudson checkout problem
body: <p>When using the Git plugin for Hudson my job always fails when fetching the latest sources from my online git repository ( git://github.com/ithena/orm2dsl.git ) .</p>
  
  <p>The git plugin first executes <code>git fetch</code> succesfully. Then it tries to execute <code>git checkout -f origin/</code> , which fails as shown below. Is this a problem with <a href="http://github.com/ithena/rose/tree/master" rel="noreferrer">my git repository</a> or is it the checkout command that makes no sense? </p>
  
  <p><strong>Git command whithout a branch set in the job configuration:</strong></p>
  
  <pre><code>git checkout -f origin/
  git checkout: updating paths is incompatible with switching branches/forcing
  Did you intend to checkout 'origin/' which can not be resolved as commit?
  </code></pre>
  
  <p><strong>Git command with branch set to master in the job configuration:</strong></p>
  
  <pre><code>git checkout -f origin/master
  git checkout: updating paths is incompatible with switching branches/forcing
  Did you intend to checkout 'origin/master' which can not be resolved as commit?
  </code></pre>
  
  <p><strong>Hudson console output:</strong></p>
  
  <pre><code>started
  Checkout
  [workspace] $ git fetch
  Checking out origin/
  [workspace] $ git checkout -f origin/
  git checkout: updating paths is incompatible with switching branches/forcing
  Did you intend to checkout 'origin/' which can not be resolved as commit?
  FATAL: Error checking out origin/
  java.lang.RuntimeException: Error checking out origin/
      at hudson.plugins.git.GitAPI.launch(GitAPI.java:101)
      at hudson.plugins.git.GitAPI.checkout(GitAPI.java:94)
      at hudson.plugins.git.GitSCM.checkout(GitSCM.java:90)
      at hudson.model.AbstractProject.checkout(AbstractProject.java:693)
      at hudson.model.AbstractBuild$AbstractRunner.checkout(AbstractBuild.java:266)
      at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:239)
      at hudson.model.Run.run(Run.java:842)
      at hudson.model.Build.run(Build.java:88)
      at hudson.model.ResourceController.execute(ResourceController.java:70)
      at hudson.model.Executor.run(Executor.java:90)
  </code></pre>
  
  <p><strong>Hudson Environment:</strong> Debian Etch, Sun JSDK 6, git 1.4.4.4, hudson latest stable download</p>