Quote volume mapping and use pwd

Signed-off-by: Stefan Scherer <stefan.scherer@docker.com>

docs/tutorial/multi-container-apps/index.md

@@ -180,7 +180,7 @@ With all of that explained, let's start our dev-ready container!
 
     ```bash hl_lines="3 4 5 6 7"
     docker run -dp 3000:3000 \
-      -w /app -v ${PWD}:/app \
+      -w /app -v "$(pwd):/app" \
       --network todo-app \
       -e MYSQL_HOST=mysql \
       -e MYSQL_USER=root \
@@ -194,7 +194,7 @@ With all of that explained, let's start our dev-ready container!
 
     ```powershell hl_lines="3 4 5 6 7"
     docker run -dp 3000:3000 `
-      -w /app -v ${PWD}:/app `
+      -w /app -v "$(pwd):/app" `
       --network todo-app `
       -e MYSQL_HOST=mysql `
       -e MYSQL_USER=root `

docs/tutorial/using-bind-mounts/index.md

@@ -40,7 +40,7 @@ So, let's do it!
 
     ```bash
     docker run -dp 3000:3000 \
-        -w /app -v ${PWD}:/app \
+        -w /app -v "$(pwd):/app" \
         node:12-alpine \
         sh -c "yarn install && yarn run dev"
     ```
@@ -49,14 +49,14 @@ So, let's do it!
 
     ```powershell
     docker run -dp 3000:3000 `
-        -w /app -v ${PWD}:/app `
+        -w /app -v "$(pwd):/app" `
         node:12-alpine `
         sh -c "yarn install && yarn run dev"
     ```
 
     - `-dp 3000:3000` - same as before. Run in detached (background) mode and create a port mapping
     - `-w /app` - sets the "working directory" or the current directory that the command will run from
-    - `-v ${PWD}:/app` - bind mount the current directory from the host in the container into the `/app` directory
+    - `-v "$(pwd):/app"` - bind mount the current directory from the host in the container into the `/app` directory
     - `node:12-alpine` - the image to use. Note that this is the base image for our app from the Dockerfile
     - `sh -c "yarn install && yarn run dev"` - the command. We're starting a shell using `sh` (alpine doesn't have `bash`) and
       running `yarn install` to install _all_ dependencies and then running `yarn run dev`. If we look in the `package.json`,

docs/tutorial/using-docker-compose/index.md

@@ -53,7 +53,7 @@ To remember, this was the command we were using to define our app container.
 
 ```bash
 docker run -dp 3000:3000 \
-  -w /app -v ${PWD}:/app \
+  -w /app -v "$(pwd):/app" \
   --network todo-app \
   -e MYSQL_HOST=mysql \
   -e MYSQL_USER=root \
@@ -67,7 +67,7 @@ If you are using PowerShell then use this command.
 
 ```powershell
 docker run -dp 3000:3000 `
-  -w /app -v ${PWD}:/app `
+  -w /app -v "$(pwd):/app" `
   --network todo-app `
   -e MYSQL_HOST=mysql `
   -e MYSQL_USER=root `
@@ -116,7 +116,7 @@ docker run -dp 3000:3000 `
           - 3000:3000
     ```
 
-1. Next, we'll migrate both the working directory (`-w /app`) and the volume mapping (`-v ${PWD}:/app`) by using
+1. Next, we'll migrate both the working directory (`-w /app`) and the volume mapping (`-v "$(pwd):/app"`) by using
    the `working_dir` and `volumes` definitions. Volumes also has a [short](https://docs.docker.com/compose/compose-file/#short-syntax-3) and [long](https://docs.docker.com/compose/compose-file/#long-syntax-3) syntax.
 
     One advantage of Docker Compose volume definitions is we can use relative paths from the current directory.