title: How does git handle folder permission?
body: <p>I'm using git version 1.5.6.3, and it seems git doesn't notice a folder's mode changes</p>
  
  <pre><code>#create a test repository with a folder with 777 mode
  :~$ mkdir -p test/folder
  :~$ touch test/folder/dummy.txt
  :~$ cd test
  :~/test$ chmod 777 folder/
  
  #init git repository
  :~/test$ git init
  Initialized empty Git repository in ~/test/.git/
  :~/test$ git add .
  :~/test$ git commit -m 'commit a directory'
  Created initial commit 9b6b21a: commit a directory
   0 files changed, 0 insertions(+), 0 deletions(-)
   create mode 100644 folder/dummy.txt
  
  #change folder permission to 744
  :~/test$ chmod 744 folder/
  :~/test$ git status 
  # On branch master
  nothing to commit (working directory clean)
  </code></pre>
  
  <p>What does <code>04000</code> stand for?</p>
  
  <pre><code>:~/test$ git ls-tree HEAD folder
  040000 tree 726c1d5f0155771348ea2daee6239791f1cd7731    folder
  </code></pre>
  
  <p>Is this normal behavior? </p>
  
  <p>How can I track folder mode changes?</p>