Update README.md to document the update process

Author: iwahbe

README.md

@@ -1,50 +1,25 @@
 # Terraform Plugin SDK
 
-This SDK enables building Terraform plugin which allows Terraform's users to manage existing and popular service providers as well as custom in-house solutions.
+This is a fork of Hashicorp's [terraform-plugin-sdk](https://github.com/hashicorp/terraform-plugin-sdk).
 
-Terraform itself is a tool for building, changing, and versioning infrastructure safely and efficiently. You can find more about Terraform on its [website](https://www.terraform.io) and [its GitHub repository](https://github.com/hashicorp/terraform).
+## Updating the fork
 
-## Documentation
+When a new version of the terraform-plugin-sdk comes out, we need to update our fork. This is necessary to avoid build errors in newer providers.
 
-See [Extending Terraform](https://www.terraform.io/docs/extend/index.html) section on the website.
+To update our fork:
+1. Checkout the latest upstream branch: `git checkout upstream-${LATEST_VERSION}`.
+2. Create a new branch: `git checkout -b upstream-${NEW_VERSION}`.
+3. Ensure that original repository is a remote and up to date:
 
-## Scope (Providers VS Core)
+   ``` shell
+   𝛌 git remote -v
+   origin  https://github.com/pulumi/terraform-plugin-sdk.git (fetch)
+   origin  https://github.com/pulumi/terraform-plugin-sdk.git (push)
+   tf      https://github.com/hashicorp/terraform-plugin-sdk.git (fetch)
+   tf      https://github.com/hashicorp/terraform-plugin-sdk.git (push)
+   𝛌 git fetch tf
+   ```
+4. Merge the new version into your branch: `git merge ${NEW_VERSION}`.
+5. Resolve any conflicts and push the new version.
 
-### Terraform Core
-
- - acts as gRPC _client_
- - interacts with the user
- - parses (HCL/JSON) configuration
- - manages state as whole, asks **Provider(s)** to mutate provider-specific parts of state
- - handles backends & provisioners
- - handles inputs, outputs, modules, and functions
- - discovers **Provider(s)** and their versions per configuration
- - manages **Provider(s)** lifecycle (i.e. spins up & tears down provider process)
- - passes relevant parts of parsed (valid JSON/HCL) and interpolated configuration to **Provider(s)**
- - decides ordering of (Create, Read, Update, Delete) operations on resources and data sources
- - ...
-
-### Terraform Provider (via this SDK)
-
- - acts as gRPC _server_
- - executes any domain-specific logic based on received parsed configuration
-   - (Create, Read, Update, Delete, Import, Validate) a Resource
-   - Read a Data Source
- - tests domain-specific logic via provided acceptance test framework
- - provides **Core** updated state of a resource or data source and/or appropriate feedback in the form of validation or other errors
-
-## Migrating to SDK v1 from built-in SDK
-
-Migrating to the standalone SDK v1 is covered on the [Plugin SDK section](https://www.terraform.io/docs/extend/plugin-sdk.html) of the website.
-
-## Versioning
-
-The Terraform Plugin SDK is a [Go module](https://github.com/golang/go/wiki/Modules) versioned using [semantic versioning](https://semver.org/).
-
-## Contributing
-
-See [`.github/CONTRIBUTING.md`](https://github.com/hashicorp/terraform-plugin-sdk/blob/master/.github/CONTRIBUTING.md)
-
-## License
-
-[Mozilla Public License v2.0](https://github.com/hashicorp/terraform-plugin-sdk/blob/master/LICENSE)
+We do not use the `master` branch for this.