How to get apt source code via VCS?

Hi, I would like to get apt source code via VCS(git,bzr,svn...). I do not find the repository of apt. I have cloned aptitude repository(git://git.debian.org/aptitude/aptitude.git) and am reading the code. I find it refers to apt class. I would like to look into apt code. Is there a repot of apt? I

Want new kernel >2.6.28 supporting ext4

Hi, all I installed debian lenny 5.0.3. The kernel is 2.6.26, I want a newer kernel image >2.6.28. Can I just "apt-get install" a new kernel? I can't find new kernel in the repository by apt-cache search "kernel-image" or search in aptitude. If there is not pre-compile kernel image in the reposit