title: How to switch android version in local repo?
body: <p>I have downloaded whole working tree with the following command:</p>
  
  <pre><code>repo init -u https://android.googlesource.com/platform/manifest
  repo sync -j8
  </code></pre>
  
  <p>After syncing successfully, I want to switch working tree to android 2.3.7.
  You see I didn't specify branch with "-b" parameter when "repo init".
  So I guess all tag info should be downloaded and I can easily switch to android 2.3.7 with the following command:</p>
  
  <pre><code>repo forall -c git checkout android-2.3.7_r1
  </code></pre>
  
  <p>But it produces many errors like:</p>
  
  <pre><code>error: pathspec 'android-2.3.7_r1' did not match any file(s) known to git.
  </code></pre>
  
  <p>So how can I switch to android 2.3.7 without "repo init -b android-2.3.7_r1" and "repo sync"  again?</p>