Split pane to cwd

lanVS's solution works out, but there may be a side effect that you don't want: If you open new tab/windows, it will reuse previous session's directory.

So if you just want the new split pane to act like that, you can do that:

1. open "Preferences", select "Profiles"
2. select the profile you want to change
3. go to "General" subtab
4. set Working Directory to "Advanced Configuration"
5. click "Edit..."
6. select "Reuse previous session's directory" for option "Working Directory for New Split Panes"

I found the answer from http://teohm.com/blog/2012/03/22/working-effectively-with-iterm2/:

Open tab/pane with current working directory

Under Profiles tab, go to General subtab, set Working Directory to “Reuse previous session’s directory”.