install: auto-add to PATH in bash install

Here is an example on how to do it (from Pulumi install script):
# Now that we have installed Pulumi, if it is not already on the path, let's add a line to the
# user's profile to add the folder to the PATH for future sessions.
if [ "${NO_EDIT_PATH}" != "true" ] && ! command -v pulumi >/dev/null; then
    # If we can, we'll add a line to the user's .profile adding ${PULUMI_INSTALL_ROOT}/bin to the PATH
    SHELL_NAME=$(basename "${SHELL}")
    PROFILE_FILE=""

    case "${SHELL_NAME}" in
        "bash")
            # Terminal.app on macOS prefers .bash_profile to .bashrc, so we prefer that
            # file when trying to put our export into a profile. On *NIX, .bashrc is
            # preferred as it is sourced for new interactive shells.
            if [ "$(uname)" != "Darwin" ]; then
                if [ -e "${HOME}/.bashrc" ]; then
                    PROFILE_FILE="${HOME}/.bashrc"
                elif [ -e "${HOME}/.bash_profile" ]; then
                    PROFILE_FILE="${HOME}/.bash_profile"
                fi
            else
                if [ -e "${HOME}/.bash_profile" ]; then
                    PROFILE_FILE="${HOME}/.bash_profile"
                elif [ -e "${HOME}/.bashrc" ]; then
                    PROFILE_FILE="${HOME}/.bashrc"
                fi
            fi
            ;;
        "zsh")
            if [ -e "${ZDOTDIR:-$HOME}/.zshrc" ]; then
                PROFILE_FILE="${ZDOTDIR:-$HOME}/.zshrc"
            fi
            ;;
    esac

    if [ -n "${PROFILE_FILE}" ]; then
        LINE_TO_ADD="export PATH=\$PATH:${PULUMI_INSTALL_ROOT}/bin"
        if ! grep -q "# add Pulumi to the PATH" "${PROFILE_FILE}"; then
            say_white "+ Adding ${PULUMI_INSTALL_ROOT}/bin to \$PATH in ${PROFILE_FILE}"
            printf "\\n# add Pulumi to the PATH\\n%s\\n" "${LINE_TO_ADD}" >> "${PROFILE_FILE}"
        fi

        EXTRA_INSTALL_STEP="+ Please restart your shell or add ${PULUMI_INSTALL_ROOT}/bin to your \$PATH"
    else
        EXTRA_INSTALL_STEP="+ Please add ${PULUMI_INSTALL_ROOT}/bin to your \$PATH"
    fi
fi

# Warn if the pulumi command is available, but it is in a different location from the current install root.
if [ "$(command -v pulumi)" != "" ] && [ "$(command -v pulumi)" != "${PULUMI_INSTALL_ROOT}/bin/pulumi" ]; then
    say_yellow
    say_yellow "warning: Pulumi has been installed to ${PULUMI_INSTALL_ROOT}/bin, but it looks like there's a different copy"
    say_yellow "         on your \$PATH at $(dirname "$(command -v pulumi)"). You'll need to explicitly invoke the"
    say_yellow "         version you just installed or modify your \$PATH to prefer this location."
fi
freelabz / secator

install: auto-add to PATH in bash install #414
