title: pod install - Podfile.lock updated
body: <p>I've just cloned a project with several pods locked.</p>
  
  <p>After a <code>pod install</code> my Podfile.lock gets modified.</p>
  
  <p>Why ?</p>
  
  <p>Isn't it supposed to be updated only if I do <code>pod update</code> ?</p>
  
  <hr>
  
  <p><strong>Podfile</strong></p>
  
  <pre class="lang-rb prettyprint-override"><code>platform :ios, '6.0'
  pod 'SVProgressHUD',    '~&gt; 0.9'
  pod 'Reachability',     '~&gt; 3.1.0'
  pod 'UIDeviceAddition', '~&gt; 1.0'
  pod 'CorePlot',         '~&gt; 1.3'
  pod 'RestKit',          '~&gt; 0.20'
  pod 'ZipArchive',       '~&gt; 1.1.0'
  </code></pre>
  
  <p><em>^- not changed -^</em></p>
  
  <p><strong>Diff</strong></p>
  
  <pre class="lang-diff prettyprint-override"><code>index c82dc53..e408a71 100644
  --- a/Podfile.lock
  +++ b/Podfile.lock
  @@ -1,5 +1,5 @@
   PODS:
  -  - AFNetworking (1.3.2)
  +  - AFNetworking (1.3.4)
     - CorePlot (1.3)
     - Reachability (3.1.1)
     - RestKit (0.20.3):
  @@ -32,14 +32,14 @@ DEPENDENCIES:
     - ZipArchive (~&gt; 1.1.0)
  
   SPEC CHECKSUMS:
  -  AFNetworking: 7f9bcd7c287a75476cd5c61e82fd3380e93e4c54
  -  CorePlot: af8307dd1fc013b3d8d97f54db8de0de6d57af84
  -  Reachability: 2be6bc2fd2bd31d97f5db33e75e4b29c79e95883
  # ...
  +  AFNetworking: 80c4e0652b08eb34e25b9c0ff3c82556fe5967b4
  +  CorePlot: f62846d49870dcb5a7fffa42f493faf836155578
  +  Reachability: 8e9635e3cb4f98e7f825e51147f677ecc694d0e7
  # ...
  
  -COCOAPODS: 0.22.3
  +COCOAPODS: 0.33.1
  </code></pre>