Updated original bash prompt with git and rbenv example with a check for the __git_ps1 function instead of existence of a git bash-completion file.

bash_prompt_with_git_and_rbenv.sh

# rbenv
export PATH="$HOME/.rbenv/bin:$PATH"
eval "$(rbenv init -)"
source ~/.rbenv/completions/rbenv.bash

# prompt with ruby version
# rbenv version | sed -e 's/ .*//'
__rbenv_ps1 ()
{
  rbenv_ruby_version=`rbenv version | sed -e 's/ .*//'`
  printf $rbenv_ruby_version
}

# prompt with git && rbenv
if [ $(type -t __git_ps1) ] && [ -f `which rbenv` ]; then
  export PS1='\[\033[01;32m\]\u@\h\[\033[01;33m\] \w$(__git_ps1) ruby=$(__rbenv_ps1) \n\[\033[01;34m\]\$\[\033[00m\] '
elif [ $(type -t __git_ps1) ]; then
  export PS1='\[\033[01;32m\]\u@\h\[\033[01;33m\] \w$(__git_ps1) \n\[\033[01;34m\]\$\[\033[00m\] '
elif [ `which rbenv` ]; then
  export PS1='\[\033[01;32m\]\u@\h\[\033[01;33m\] \w ruby=$(__rbenv_ps1) \n\[\033[01;34m\]\$\[\033[00m\] '
else
  export PS1='\[\033[01;32m\]\u@\h\[\033[01;33m\] \w \n\[\033[01;34m\]\$\[\033[00m\] '
fi