update: instructions to update openapi (#350)

* Add openapi submodule instructions to README.md

Add instructions for updating the influx-cli/openapi git submodule when regenerating the CLI.

* update: instructions to update openapi

Add instructions to update and regenerate influx-cli/openapi when changing commits.

Author: jstirnaman

README.md

@@ -9,17 +9,44 @@ This repository decouples the `influx` CLI from the OSS `influxdb` codebase. Our
 2. Enable faster turn-around on fixes/features that only affect the CLI
 3. Allow the CLI to be built & released for a wider range of platforms than the server can support
 
-## Building
+## Building the CLI
 
-Run `make` or `make influx` to build the CLI. The output binary will be written to `bin/$(GOOS)/influx`.
+Follow these steps to build the CLI. If you're updating your CLI build, see *Updating openapi* below.
+1. Clone this repo (influx-cli) and change to your _influx-cli_ directory.
 
-### Regenerating OpenAPI client
+   ```
+   git clone [email protected]:influxdata/influx-cli.git
+   cd influx-cli
+   ```
+   
+2. Build the CLI. The `make` and `make influx` commands write the new binary to `bin/$(GOOS)/influx`.
+   
+   ```
+   make
+   ```
+   
+### Updating openapi
 
+If you change or update your branch, you may also need to update `influx-cli/openapi` and regenerate the client code.
+`influx-cli/openapi` is a Git submodule that contains the underlying API contracts and client used by the CLI.
 We use [`OpenAPITools/openapi-generator`](https://github.com/OpenAPITools/openapi-generator) to generate
-the underlying HTTP client used by the CLI. Run `make openapi` to re-generate the code. You'll need Docker
-running locally for the script to work.
+the HTTP client.
 
-## Running
+To update, run the following commands in your `influx-cli` repo:
+
+1. Update the _openapi_ Git submodule. The following command pulls the latest commits for the branch and all submodules.
+
+   `git pull --recurse-submodules`
+   
+2. With [Docker](https://docs.docker.com/get-docker/) running locally, regenerate _openapi_.
+
+   `make openapi`
+   
+3. Rebuild the CLI
+
+   `make`
+ 
+## Running the CLI
 
 After building, use `influx -h` to see the list of available commands.