Bash prompt that shows git branch, if in a git directory

.bashrc

# Shows the git branch we're currently on, if in a git directory
function gitbranch() {
	perl -e '
		my $output = `git branch 2> /dev/null`;
		my ($branch) = $output =~ /\* ([\S]+)/;
		if ($branch) { 
			print "[$branch]"; 
		}
	';
}

export PS1='[\t] ${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[01;34m\] \w `gitbranch`\$\[\033[00m\] '