update cgit README.md

Signed-off-by: Gong Sophia <sophia.gong@intel.com>

cgit/README.md

@@ -1,27 +1,88 @@
-# cgit
-==========
-This provides a Clear Linux* cgit service
+# Clear Linux* OS `cgit` container image
 
-Build
------
-```
-docker build -t clearlinux/cgit .
-```
+<!-- Required -->
+## What is this image?
 
-Or just pull it from Dockerhub
----------------------------
-```
-docker pull clearlinux/cgit
-```
+`clearlinux/cgit` is a Docker image with `cgit` running on top of the
+[official clearlinux base image](https://hub.docker.com/_/clearlinux). 
 
-Start cgit Container
------------------------
-```
-docker run -p 80:80 -v <git repo path>:/var/www/cgit clearlinux/cgit
-```
+<!-- application introduction -->
+> [Cgit](https://git.zx2c4.com/cgit/) is a hyperfast web frontend for git repositories written in C.
 
-Extra Build ARGs
-----------------
-- ``swupd_args`` Specifies [SWUPD](https://github.com/clearlinux/swupd-client/blob/master/docs/swupd.1.rst#options) flags
+For other Clear Linux* OS
+based container images, see: https://hub.docker.com/u/clearlinux
 
-Default build args in Docker are on: https://docs.docker.com/engine/reference/builder/#arg
+## Why use a clearlinux based image?
+
+<!-- CL introduction -->
+> [Clear Linux* OS](https://clearlinux.org/) is an open source, rolling release
+> Linux distribution optimized for performance and security, from the Cloud to
+> the Edge, designed for customization, and manageability.
+
+Clear Linux* OS based container images use:
+* Optimized libraries that are compiled with latest compiler versions and
+  flags.
+* Software packages that follow upstream source closely and update frequently.
+* An aggressive security model and best practices for CVE patching.
+* A multi-staged build approach to keep a reduced container image size.
+* The same container syntax as the official images to make getting started
+  easy. 
+
+To learn more about Clear Linux* OS, visit: https://clearlinux.org.
+
+<!-- Required -->
+## Deployment:
+
+### Deploy with Docker
+The easiest way to get started with this image is by simply pulling it from
+Docker Hub. 
+
+
+1. Pull the image from Docker Hub: 
+    ```
+    docker pull clearlinux/cgit
+    ```
+
+2. Start a container using the examples below:
+
+    ```
+    docker run -p 80:80 -v <git repo path>:/var/www/cgit clearlinux/cgit
+    ```
+    
+<!-- Optional -->
+### Deploy with Kubernetes
+
+<!-- Required -->
+## Build and modify:
+
+The Dockerfiles for all Clear Linux* OS based container images are available at
+https://github.com/clearlinux/dockerfiles. These can be used to build and
+modify the container images.
+
+1. Clone the clearlinux/dockerfiles repository.
+    ```
+    git clone https://github.com/clearlinux/dockerfiles.git
+    ```
+
+2. Change to the directory of the application:
+    ```
+    cd cgit/
+    ```
+
+3. Build the container image:
+    ```
+    docker build -t clearlinux/cgit .
+    ```
+
+   Refer to the Docker documentation for [default build arguments](https://docs.docker.com/engine/reference/builder/#arg).
+   Additionally:
+   
+   - `swupd_args` - specifies arguments to pass to the Clear Linux* OS software
+     manager. See the [swupd man pages](https://github.com/clearlinux/swupd-client/blob/master/docs/swupd.1.rst#options)
+     for more information.
+
+<!-- Required -->
+## Licenses
+
+All licenses for the Clear Linux* Project and distributed software can be found
+at https://clearlinux.org/terms-and-policies