title: pod repo update failed: Cannot do hard reset with paths
body: <p>When I'm running </p>
  
  <pre><code>proxychains4 pod repo update
  </code></pre>
  
  <p>I got the following output</p>
  
  <pre><code>[proxychains] config file found: /usr/local/Cellar/proxychains-ng/4.10/etc/proxychains.conf
  [proxychains] preloading /usr/local/Cellar/proxychains-ng/4.10/lib/libproxychains4.dylib
  [proxychains] DLL init: proxychains-ng 4.10
  [proxychains] DLL init: proxychains-ng 4.10
  [proxychains] DLL init: proxychains-ng 4.10
  [proxychains] DLL init: proxychains-ng 4.10
  [proxychains] DLL init: proxychains-ng 4.10
  [proxychains] DLL init: proxychains-ng 4.10
  Updating spec repo `master`
  [proxychains] DLL init: proxychains-ng 4.10
  [proxychains] DLL init: proxychains-ng 4.10
  [proxychains] Strict chain  ...  127.0.0.1:1080  ...  api.github.com:443  ...  OK
  [proxychains] DLL init: proxychains-ng 4.10
  [proxychains] DLL init: proxychains-ng 4.10
    $ /usr/local/bin/git -C /Users/linxi/.cocoapods/repos/master fetch origin
    [proxychains] DLL init: proxychains-ng 4.10
    [proxychains] DLL init: proxychains-ng 4.10
    [proxychains] Strict chain  ...  127.0.0.1:1080  ...  github.com:443  ...  OK
    [proxychains] DLL init: proxychains-ng 4.10
    [proxychains] DLL init: proxychains-ng 4.10
    [proxychains] DLL init: proxychains-ng 4.10
    From https://github.com/CocoaPods/Specs
       1eaabbe..7cc75a2  master     -&gt; origin/master
    [proxychains] DLL init: proxychains-ng 4.10
    $ /usr/local/bin/git -C /Users/linxi/.cocoapods/repos/master rev-parse --abbrev-ref HEAD
    [proxychains] DLL init: proxychains-ng 4.10
    master
    $ /usr/local/bin/git -C /Users/linxi/.cocoapods/repos/master reset --hard origin/master [proxychains] DLL init: proxychains-ng 4.10
    [proxychains] DLL init: proxychains-ng 4.10
    fatal: Cannot do hard reset with paths.
  [!] CocoaPods was not able to update the `master` repo. If this is an unexpected issue and persists you can inspect it running `pod repo update --verbose`
  </code></pre>
  
  <p>However, if I run git manually</p>
  
  <pre><code>proxychains4 /usr/local/bin/git -C /Users/linxi/.cocoapods/repos/master reset --hard origin/master
  </code></pre>
  
  <p>Everything works well.</p>
  
  <p>I have to use proxychains to connect github.</p>
  
  <p>I'm running cocoapods version 1.2.0/git version 2.7.0.</p>