Do a git checkout of Dragonfly BSD Hammer2 File System

1. Clone the main Dragonfly BSD git repo (approx. 750MB)

$git clone git://git.dragonflybsd.org/dragonfly.git dragonfly
$cd dragonfly

2. List all branches

$git branch -a
* master
  remotes/origin/DragonFly_RELEASE_1_10
  remotes/origin/DragonFly_RELEASE_1_12
  remotes/origin/DragonFly_RELEASE_1_2
  remotes/origin/DragonFly_RELEASE_1_4
  remotes/origin/DragonFly_RELEASE_1_6
  ....
  remotes/origin/HEAD -> origin/master
  remotes/origin/doc
  remotes/origin/hammer2   <======================== HAMMER2
  remotes/origin/master
  remotes/origin/netmp
  ....

3. Checkout the Hammer2 branch

$git checkout hammer2
cd sys/vfs/hammer2