docs: first version of user manual

Signed-off-by: Sam Alba <sam.alba@gmail.com>

docs/user/user.md

@@ -6,4 +6,102 @@ sidebar_label: User Manual
 
 # User Manual
 
-TODO
+In this part, you will learn how to deploy a simple [React](https://reactjs.org/) application. This is an introduction before you [learn how to program dagger](/programming).
+
+You will learn how to use the most common dagger commands.
+
+## Before we start
+
+First, you'll need to make sure [you have installed dagger on your local machine](/install).
+
+## Let's deploy our first application
+
+**Step 1**: Clone the example repository
+
+```sh
+git clone https://github.com/dagger/examples.git
+```
+
+**Step 2**: Go the todoapp directory
+
+`todoapp` is a simple Todo-list application written in Javascript using [React](https://reactjs.org/).
+
+Go to the app directory:
+
+```sh
+cd ./examples/todoapp
+```
+
+**Step 3**: Decrypt the inputs
+
+The example app contains encrypted secrets and other pre-configured inputs, here is how to decrypt them:
+
+```sh
+dagger input list || curl -sfL https://releases.dagger.io/examples/key.txt >> ~/.config/dagger/keys.txt
+```
+
+**Step 4**: Deploy!
+
+```sh
+dagger up
+```
+
+At the end of the deploy, you should see a list of outputs. There is one that is named `url`. This is the URL where our app has been deployed. If you go to this URL, you should see your application live!
+
+## Change some code and re-deploy
+
+This repository is already configured to deploy the code in the directory `./todoapp`, so you can change some code (or replace the app code with another react app!) and re-run the following command to re-deploy when you want your changes to be live:
+
+```sh
+dagger up
+```
+
+## Under the hood
+
+This example showed you how to deploy and develop on an application that is already configured with dagger. Now, let's learn a few concepts to help you understand how this was put together.
+
+### The Environment
+
+An Environment holds the entire deployment configuration.
+
+You can list existing environment from the `./todoapp` directory:
+
+```sh
+dagger list
+```
+
+You should see an environment named `s3`. You can have many environments within your app. For instance one for `staging`, one for `dev`, etc...
+
+Each environment can have different kind of deployment code. For example, a `dev` environment can deploy locally, a `staging` environment can deploy to a remote infrastructure, and so on.
+
+### The plan
+
+The plan is the deployment code, that includes the logic to deploy the local application to an AWS S3 bucket. From the `todoapp` directory, you can list the code of the plan:
+
+```sh
+ls -l .dagger/env/s3/plan/
+```
+
+Any code change to the plan will be applied during the next `dagger up`.
+
+### The inputs
+
+The plan can define one or several `inputs` in order to take some information from the user. Here is how to list the current inputs:
+
+```sh
+dagger input list
+```
+
+The inputs are persisted inside the `.dagger` directory and pushed to your git repository. That's why this example application worked out of the box.
+
+### The outputs
+
+The plan defines one or several `outputs`. They can show useful information at the end of the deployment. That's how we read the deploy `url` at the end of the deployment. Here is the command to list all inputs:
+
+```sh
+dagger output list
+```
+
+## What's next?
+
+At this point, you have deployed your first application using dagger and learned some dagger commands. You are now ready to [learn more about how to program dagger](/programming).