direnv enabler script, inspired by "basher" install script

enable_direnv.sh

#!/usr/bin/env bash
## direnv enabler script, inspired by "basher" install script

die() {
  echo "!! $1 " >&2
  echo "!! -----------------------------" >&2
  exit 1
}

## stop if direnv is not installed
command -v direnv >/dev/null 2>&1 || die "I require direnv but it's not installed.  Aborting."

## now check what shell is running
shell_type=$(basename "$SHELL")
echo ". detected shell type: $shell_type"
case "$shell_type" in
bash)  startup_type="simple" ; startup_script="$HOME/.bashrc" ;;
zsh)   startup_type="simple" ; startup_script="$HOME/.zshrc"  ;;
sh)    startup_type="simple" ; startup_script="$HOME/.profile";;
fish)  startup_type="fish"   ; startup_script="$HOME/.config/fish/config.fish"  ;;
*)     startup_type="?"      ; startup_script="" ;   ;;
esac

## startup script should exist already
[[ -n "$startup_script" && ! -f "$startup_script" ]] && die "startup script [$startup_script] does not exist"

## direnv_keyword will allow us to remove the lines upon uninstall
direnv_keyword="direnv5ea843"

## now add the basher initialisation lines to the user's startup script
echo ". add direnv initialisation to [$startup_script]"
if [[ "$startup_type" == "simple" ]]; then
  (
    echo "eval \"\$(direnv hook $shell_type)\"             ##$direnv_keyword"
    echo "eval \"\$(direnv stdlib)\"             ##$direnv_keyword"
  ) >>"$startup_script"
elif [[ "$startup_type" == "fish" ]]; then
  (
    echo "status --is-interactive; and . (direnv hook - $shell_type | psub)    ##$direnv_keyword"
    echo "status --is-interactive; and . (direnv stdlib | psub)    ##$direnv_keyword"
  ) >>"$startup_script"
else
  die "unknown shell [$shell_type] - can't initialise"
fi

## script is finished
echo "direnv config is installed - open a new terminal window to start using it"