Update README

README.md

@@ -3,7 +3,7 @@
 Deploy your application from a CI/CD pipeline via `cURL` + JWT auth.
 
 ```
-$ curl -s -H "Authorization: bearer abc..." https://example.com/your/rollout/path
+$ curl -s -d '{"git-branch": "main"}' -H "Authorization: bearer abc..." https://example.com/your/rollout/path
 Rollout complete
 ```
 
@@ -13,7 +13,7 @@ Instead of managing SSH keys in your CI/CD for accounts that have privileged acc
 
 Requires creating a JWT from your CI provider, and sending that token to this service running in your deployment environment to trigger a deployment script.
 
-Also requires a `rollout.sh` script that can handle all the command needing ran to rollout your software.
+Also requires a `rollout.sh` script that can handle all the commands needing ran to rollout your software.
 
 ## Install
 
@@ -29,7 +29,7 @@ $ docker run \
 
 ## OIDC Provider examples
 
-This service requires two envionrment variables.
+This service requires two environment variables.
 
 - `JWKS_URI` - the URL of the OIDC Provider's [JSON Web Key (JWK) set document](https://www.rfc-editor.org/info/rfc7517). This is used to ensure the JWT was signed by the provider.
 - `JWT_AUD` - the audience set in the JWT token.
@@ -40,6 +40,28 @@ This service requires two envionrment variables.
 - `ROLLOUT_CMD` (default: `/bin/bash`) - the command to execute a rollout
 - `ROLLOUT_ARGS` (default: `/rollout.sh` ) - the args to pass to `ROLLOUT_CMD`
 
+## Dynamic environment variables for ROLLOUT_CMD
+
+There are a few environment variables you can make available to your rollout command.
+
+These environment variables can be passed to the cURL command when rolling out your changes.
+
+For example, if you want your rollout script to have the git branch that is being deployed you can pass that in the rollout like so:
+
+```
+$ curl -s -d '{"git-branch": "main"}' -H "Authorization: bearer abc..." https://example.com/your/rollout/path
+```
+
+These are the environment variables currently supported, keyed by their respective JSON key name:
+
+- `docker-image` **:** `DOCKER_IMAGE`
+-	`docker-tag` **:** `DOCKER_TAG`
+-	`git-repo` **:** `GIT_REPO`
+-	`git-branch` **:** `GIT_BRANCH`
+-	`rollout-arg1` **:** `ROLLOUT_ARG1`
+-	`rollout-arg2` **:** `ROLLOUT_ARG2`
+-	`rollout-arg3` **:** `ROLLOUT_ARG3`
+
 ### GitHub
 
 ```