About *git clone --depth=n* puzzle

Hi Guys,

I think I have got some trouble when I use `git clone --depth=n` command. Take a real repo for example:

`git clone https://github.com/douglarek/vimrc.git --depth=1`

then I use `git log`:
  
```  
    commit d04ca09ecc723739123fae11ad56784eb0c9b36a
    Author: Lingchao Xin <douglarek@outlook.com>
    Date:   Fri Jun 7 09:39:22 2013 +0800

        Update vnudle to master branch, add wm shortcut, pylint optimization

    commit c66d827dc212f6ae8aab6b5c44631564bcbe2acd
    Author: icocoa <lingchax@outlook.com>
    Date:   Tue Mar 12 01:36:34 2013 -0700

        Merge pull request #1 from douglarek/master

        Add markdown, flake8, pylint plugin

```
    but when I clone it with `file://`:

    git clone https://github.com/douglarek/vimrc.git
    git clone file://vimrc.git --depth=1 vimrc1

    I got this log:
```
    commit d04ca09ecc723739123fae11ad56784eb0c9b36a
Author: Lingchao Xin <douglarek@outlook.com>
Date:   Fri Jun 7 09:39:22 2013 +0800

    Update vnudle to master branch, add wm shortcut, pylint optimization
```

so the two results are not same, is it a bug? or it should be so?

My os is openSUSE 12.3 and git version 1.8.3.4; and myabe it occured in git 1.8.1.4 +.

Thanks and Best regards

Lingchao Xin