Make using docker on macOS nicer

utilities/utilities.plugin.zsh

@@ -1,5 +1,7 @@
 # A collection of various shell utilities.
 
+autoload colors && colors
+
 # Detect the type and extract an archive file.
 extract() {
   if [ -f $1 ]; then
@@ -16,9 +18,38 @@ extract() {
       *.zip)       unzip $1       ;;
       *.Z)         uncompress $1  ;;
       *.7z)        7zr x $1       ;;
-      *)           echo "error: unable to extract '$1'" ;;
+      *)           echo "$fg[red]error:$reset_color unable to extract '$1'" ;;
     esac
   else
-    echo "error: file not found '$1'"
+    echo "$fg[red]error:$reset_color file not found '$1'"
   fi
 }
+
+if which docker-machine &> /dev/null; then
+  # Wrap the docker command to print a message if a docker-machine is not
+  # running, rather than just stating it can not find it's socket.
+  docker() {
+    command docker "$@"
+    if ! docker-machine active &> /dev/null; then
+      echo "$fg[red]error:$reset_color no active host found, run:" \
+           "docker-machine start <machine>"
+      return 1
+    fi
+  }
+
+  # Wrap the docker-machine command to automatically update the environment.
+  # When a machine is started, set the environment variables provided by
+  # docker-machine env <machine>. When a machine is stopped, unset the same
+  # variables.
+  docker-machine() {
+    command docker-machine "$@"
+    if [ "start" = "$1" ]; then
+      eval `docker-machine env $2`
+    elif [ "stop" = "$1" ]; then
+      unset DOCKER_MACHINE_NAME
+      unset DOCKER_CERT_PATH
+      unset DOCKER_HOST
+      unset DOCKER_TLS_VERIFY
+    fi
+  }
+fi