Set the default directory in mac terminal

I only use terminal (mac) for git, and I only use git for one directory. Is it possible to set the default directory (the directory when terminal is opened) to the directory where I use git, and if so how?

As of Mac OS X Lion 10.7, Terminal supports Resume and by default will automatically restore terminals you had open when you quit, restoring their working directories. So, you can just open a new terminal and cd to your git directory, then leave the window open when you Quit. Each time you reopen Terminal, the terminal will be there, in the same directory. (This works for bash by default. If you're using some other shell, you'll need to adapt the code in /etc/bashrc to your shell. I've posted code for zsh in my answer to Resume Zsh-Terminal (OS X Lion) on SuperUser.)

You can also arrange for Terminal to start a shell in a particular directory. You can customize or create a "Settings Profile" to issue a "cd" command when it starts:

Terminal > Preferences > Settings > [profile] > Shell > Startup > Run command

Enable "Run command" and "Run inside shell", then set the command to cd your_git_directory. When you open a new terminal with that profile, it will go to your git directory.

I recommend you Duplicate the current default profile (if you've never changed it, the default is "Basic") using the Action ("gear") menu at the bottom of the profiles list, then customize that profile.

Finally, to have it automatically open a terminal with this profile when you open Terminal, set

Terminal > Preferences > Startup > On Startup, open

to your custom profile. (On Lion, Resume will restore windows that were open when you quit, rather than perform the startup action. As I mentioned, you can just leave this terminal open when you Quit and it will be restored when you open Terminal again. Or, you can press the Option modifier key when quitting; the Quit menu item will change to "Quit and Discard Windows" and the next time you open Terminal it will perform the startup action.)

I like to have 'New windows open with: Same Working Directory'. All answers I've found for this question (many SO's) will break that setting by always going to the new home directory. Below is what I use at the top of my .profile (or .bashrc, etc).

export START="/Users/michael/my/starting/directory"
if [[ $PWD == $HOME ]]; then
    cd $START
fi

This will see if you are in your HOME directory only on launch, and if so change to your new START directory. That way new windows won't automatically run this command.

The only caveat is if you're in your actual HOME directory and open a new window, it will take you to START. Which is expected.