Add docker-machine plugin (#4782)

plugins/docker-machine/README.md

+# docker-machine plugin for oh my zsh
+
+### Usage
+
+#### docker-vm
+Will create a docker-machine with the name "dev" (required only once)
+To create a second machine call "docker-vm foobar" or pass any other name
+
+#### docker-up
+This will start your "dev" docker-machine (if necessary) and set it as the active one
+To start a named machine use "docker-up foobar"
+
+#### docker-switch dev
+Use this to activate a running docker-machine (or to switch between multiple machines)
+You need to call either this or docker-up when opening a new terminal
+
+#### docker-stop
+This will stop your "dev" docker-machine
+To stop a named machine use "docker-stop foobar"
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plugins/docker-machine/docker-machine.plugin.zsh

+DEFAULT_MACHINE="default"
+
+docker-up() {
+    if [ -z "$1" ]
+    then
+        docker-machine start "${DEFAULT_MACHINE}"
+        eval $(docker-machine env "${DEFAULT_MACHINE}")
+    else
+        docker-machine start $1
+        eval $(docker-machine env $1)
+    fi
+    echo $DOCKER_HOST
+}
+docker-stop() {
+    if [ -z "$1" ]
+    then
+        docker-machine stop "${DEFAULT_MACHINE}"
+    else
+        docker-machine stop $1
+    fi
+}
+docker-switch() {
+    eval $(docker-machine env $1)
+    echo $DOCKER_HOST
+}
+docker-vm() {
+    if [ -z "$1" ]
+    then
+        docker-machine create -d virtualbox --virtualbox-disk-size 20000 --virtualbox-memory 4096 --virtualbox-cpu-count 2 "${DEFAULT_MACHINE}"
+    else
+        docker-machine create -d virtualbox --virtualbox-disk-size 20000 --virtualbox-memory 4096 --virtualbox-cpu-count 2 $1
+    fi
+}
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