Add docs for reading Dockerfile from stdin.
@@ -344,6 +344,13 @@ $ docker build -f Dockerfile.debug .
This will use a file called `Dockerfile.debug` for the build instructions
instead of `Dockerfile`.
+```bash
+$ curl example.com/remote/Dockerfile | docker build -f - .
+```
+
+The above command will use the current directory as the build context and read
+a Dockerfile from stdin.
+
```bash
$ docker build -f dockerfiles/Dockerfile.debug -t myapp_debug .
$ docker build -f dockerfiles/Dockerfile.prod -t myapp_prod .
