Display git branch in zsh on MacOS

set_git_shell.sh

# set rc file
SHELL=$(echo ${SHELL})
if [ ${SHELL} == "/bin/bash" ]; then
    RC="/Users/${USER}/.bashrc"
elif [ ${SHELL} == "/bin/zsh" ]; then
    RC="/Users/${USER}/.zshrc"
else
    echo "${SHELL} not supported"
fi

read -r -d '' SHOW_GIT_BRANCH <<'EOF'
    # Load version control information
    autoload -Uz vcs_info
    precmd() { vcs_info }

    # Format the vcs_info_msg_0_ variable
    zstyle ':vcs_info:git:*' formats 'on branch %b'

    # Set up the prompt (with git branch name)
    setopt PROMPT_SUBST
    PROMPT='%n in ${PWD/#$HOME/~} ${vcs_info_msg_0_} > '
EOF

GIT_BRANCH_SET=$(cat ${RC} | grep -q PROMPT=)
if [ ${?} == 1 ] && [ ${SHELL} == "/bin/zsh" ]; then
    echo ${SHOW_GIT_BRANCH} >> ${RC}
else
    echo "git shell settings already exist"
fi