title: Git change default umask when update file
body: <p>I have a problem with Git. I searched for a solution in Google and in StackOverflow but nothing helps.</p>
  
  <p>The problem is that every time git updates some file in the working directory (when I checkout branches or I merge a branch, etc.) then the file permissions are changed such that the "writable to group" flag is added.
  And my apache shows "Error 500" for the file if it is writable to group.</p>
  
  <p>Example:
  I have a file index.php.  Permissions are "-rwxr-xr-x". Current (active) branch is master. This file was changed in the branch "develop".
  I execute "git checkout develop" and the file index.php gets permissions "-rwxrwxr-x" (writable to group is added). And my site stops working. As apache doesn't allow this flag in php files (I don't know why but I can not change this).</p>
  
  <p>Every time when I execute "git checkout develop" I need to execute also "chmod g-w index.php". I don't like to execute two commands (and sometimes I forget to execute this and my site doesn't work).</p>
  
  <p>What can I do to solve this problem?
  I think this is something related to umask. I did some tricks I found on web, but nothing works.</p>
  
  <p>Thanks.</p>