feat: add installation doc (#95)

Author: Noah Hanjun Lee

docs/concepts/deployment.md

@@ -12,6 +12,6 @@ With approval, Gitploy waits until it matches the required approving approvals.
 
 Rollback is the best way to recover while you fix the problems. Gitploy supports the rollback, and you can choose one of the successful deployments to rollback. 
 
-For best practice, you should lock the repository to block deploying by others. And the admin user has to take care of the repository until finishing to fix the problems.
+For best practice, you should lock the repository to block deploying by others until finishing to fix the problems. Gitploy provide the 'lock' feature in UI and Chatops.
 
 *Note that if the ref of the selected deployment is a branch, Gitploy automatically references the commit SHA to prevent deploying the head of the branch.*

docs/images/github-oauth.png

@@ -1,5 +1,7 @@
 # Gitploy
 
-Gitploy helps **you can build the advanced deployment pipeline in minutes**. It enables teams to deploy the application with lower risk and faster when to trigger a deployment. And the pipeline is configured with a simple, easy‑to‑read file that you commit to your git repository.
+![Gitploy](./images/gitploy.png)
+
+---
 
-![Gitploy](./images/gitploy.png)
+Gitploy helps **you can build the advanced deployment pipeline in minutes**. It enables teams to deploy the application with lower risk and faster when to trigger a deployment. And the pipeline is configured with a simple, easy‑to‑read file that you commit to your git repository.

docs/index.md

@@ -1 +1,62 @@
-# Installation
+# Installation
+
+This article explains how to install the Gitploy server for GitHub.
+
+## Step 1: Preparation
+
+### Provision an instance
+
+The server should be installed on a server or virtual machine with standard http and https ports open. 
+
+### Create an OAuth Application
+
+[Create a GitHub OAuth application.](https://docs.github.com/en/developers/apps/building-oauth-apps/creating-an-oauth-app) The Client Key and Client Secret are used to authorize access to GitHub resources.
+
+*The authorization callback URL must match with the format:* `GITPLOY_SERVER_PROTO://GITPLOY_SERVER_HOST/signin`.
+
+Figure) Github OAuth
+
+![Github OAuth](../images/github-oauth.png)
+
+## Step 2: Download
+
+The server is distributed as a Docker image. The image is self-contained and does not have any external dependencies. We recommend to use the last version.
+
+```
+docker pull gitployio/gitploy:0.2
+```
+
+## Step 3: Configuration
+
+The server is configured using environment variables. This article only configures with least environment. See [Configurations](../references/configurations.md) for a complete list of configuration options.
+
+* **GITPLOY_SERVER_HOST**: 
+Required string value configures the user-facing hostname. This value is used to create webhooks and redirect urls. 
+
+* **GITPLOY_SERVER_PROTO**: 
+Optional string value configures the user-facing protocol. This value is used to create webhooks and redirect urls. It can be one of them: `http` or `https`, and the default value is `https`.
+
+* **GITPLOY_GITHUB_CLIENT_ID**:
+Required string value configures the GitHub OAuth client id. This is used to authorize access to GitHub on behalf of a Gitploy user.
+
+* **GITPLOY_GITHUB_CLIENT_SECRET**:
+Required string value configures the GitHub OAuth client secret. This is used to authorize access to GitHub on behalf of a Gitploy user.
+
+## Step 4: Start server
+
+The server container can be started with the below command. The container is configured through environment variables.
+
+```shell
+docker run \
+  --volume=/var/lib/gitploy:/data \
+  --env=GITPLOY_SERVER_HOST={{GITPLOY_SERVER_HOST}} \
+  --env=GITPLOY_SERVER_PROTO={{GITPLOY_SERVER_PROTO}} \
+  --env=GITPLOY_GITHUB_CLIENT_ID={{GITPLOY_GITHUB_CLIENT_ID}} \
+  --env=GITPLOY_GITHUB_CLIENT_SECRET={{GITPLOY_GITHUB_CLIENT_SECRET}} \
+  --publish=80:80 \
+  --publish=443:443 \
+  --restart=always \
+  --detach=true \
+  --name=gitploy \
+  gitployio/gitploy:0.2
+```