Splitting out the cli command into parts.

Signed-off-by: Mary Anthony <mary@docker.com>

docs/reference/commandline/pull.md

@@ -0,0 +1,51 @@
+<!--[metadata]>
++++
+title = "pull"
+description = "The pull command description and usage"
+keywords = ["pull, image, hub, docker"]
+[menu.main]
+parent = "smn_cli"
+weight=1
++++
+<![end-metadata]-->
+
+# pull
+
+    Usage: docker pull [OPTIONS] NAME[:TAG] | [REGISTRY_HOST[:REGISTRY_PORT]/]NAME[:TAG]
+
+    Pull an image or a repository from the registry
+
+      -a, --all-tags=false    Download all tagged images in the repository
+
+Most of your images will be created on top of a base image from the
+[Docker Hub](https://hub.docker.com) registry.
+
+[Docker Hub](https://hub.docker.com) contains many pre-built images that you
+can `pull` and try without needing to define and configure your own.
+
+It is also possible to manually specify the path of a registry to pull from.
+For example, if you have set up a local registry, you can specify its path to
+pull from it. A repository path is similar to a URL, but does not contain
+a protocol specifier (`https://`, for example).
+
+To download a particular image, or set of images (i.e., a repository),
+use `docker pull`:
+
+    $ docker pull debian
+    # will pull the debian:latest image and its intermediate layers
+    $ docker pull debian:testing
+    # will pull the image named debian:testing and any intermediate
+    # layers it is based on.
+    $ docker pull debian@sha256:cbbf2f9a99b47fc460d422812b6a5adff7dfee951d8fa2e4a98caa0382cfbdbf
+    # will pull the image from the debian repository with the digest
+    # sha256:cbbf2f9a99b47fc460d422812b6a5adff7dfee951d8fa2e4a98caa0382cfbdbf
+    # and any intermediate layers it is based on.
+    # (Typically the empty `scratch` image, a MAINTAINER layer,
+    # and the un-tarred base).
+    $ docker pull --all-tags centos
+    # will pull all the images from the centos repository
+    $ docker pull registry.hub.docker.com/debian
+    # manually specifies the path to the default Docker registry. This could
+    # be replaced with the path to a local registry to pull from another source.
+    # sudo docker pull myhub.com:8080/test-image
+