improve piston shell script

- fix portability & using piston within a symlink
- only install cli npm modules on update or first use
- allow building packages with custom builder
- fix all shellchecks except SC2164

piston

@@ -1,7 +1,10 @@
 #!/usr/bin/env bash
-cd "$(dirname "$0")"
 
-PISTON_ENV=$(cat .piston_env || echo dev)
+EXECUTION_PATH="$PWD"
+PISTON_PATH="$(dirname "$(realpath "$0")")"
+
+cd "$PISTON_PATH"
+PISTON_ENV=$(cat .piston_env 2> /dev/null || echo dev)
 
 docker_compose(){
     if [ -f "docker-compose.$PISTON_ENV.yaml" ]; then
@@ -32,13 +35,14 @@ case $1 in
         echo
         echo "Development Commands:"
 
-        if [ $PISTON_ENV == dev ]; then
+        if [ "$PISTON_ENV" == dev ]; then
 
-        echo " clean-pkgs                     Clean any package build artifacts on disk"
-        echo " clean-repo                     Remove all packages from local repo"
-        echo " build-pkg <package> <version>  Build a package"
-        echo " rebuild                        Build and restart the docker container"
-        echo " lint                           Lint the codebase using prettier"
+        echo " clean-pkgs                              Clean any package build artifacts on disk"
+        echo " clean-repo                              Remove all packages from local repo"
+        echo " list-pkgs                               Lists all packages that can be built"
+        echo " build-pkg <package> <version> [builder] Build a package [with desired builder image]"
+        echo " rebuild                                 Build and restart the docker container"
+        echo " lint                                    Lint the codebase using prettier"
 
         else
 
@@ -56,7 +60,7 @@ case $1 in
     restart) docker_compose restart ;;
     start)
         rm -f .git/hooks/pre-commit
-        ln -s $(realpath $(dirname "$0"))/pre-commit .git/hooks/pre-commit
+        ln -s "$PISTON_PATH/pre-commit" "$PISTON_PATH/.git/hooks/pre-commit"
         docker_compose up -d
         ;;
     stop) docker_compose down ;;
@@ -66,6 +70,7 @@ case $1 in
 
     update)
         git pull
+        cd cli && npm i > /dev/null && cd -
         docker_compose pull
         docker_compose up -d
         ;;
@@ -73,12 +78,15 @@ case $1 in
     clean-pkgs) git clean -fqXd packages ;;
     clean-repo) git clean -fqXd repo ;;
 
+    list-pkgs) find packages -depth 2 | awk -F/ '$2 && $3{ print $2 "-" $3 }' | column ;;
+
     build-pkg)
         PKGSLUG="$2-$3"
+        BUILDER="${4:-piston-repo-builder}"
         echo "Building $PKGSLUG"
         echo "Ensuring latest builder image"
-        docker build repo -t piston-repo-builder
-        docker run --rm -v "$(realpath $(dirname "$0")):/piston" piston-repo-builder --no-server $PKGSLUG
+        docker build repo -t "$BUILDER"
+        docker run --rm -v "$PWD:/piston" "$BUILDER" --no-server "$PKGSLUG"
         ;;
 
     lint)
@@ -86,9 +94,8 @@ case $1 in
         npx prettier --ignore-unknown --write .
         ;;
     *)
-        cd cli
-        npm i > /dev/null
-        cd ../
-        node cli/index.js "$@"
-    ;;
+        [ -d ./cli/node_modules ] || npm i > /dev/null
+        cd "$EXECUTION_PATH"
+        node "${PISTON_PATH}/cli/index.js" "$@"
+        ;;
 esac