Merge pull request github#15622 from FlashSheridan/patch-3

Add warning about env vars defined via others

Author: lecoursen

content/actions/using-workflows/workflow-syntax-for-github-actions.md

@@ -184,7 +184,9 @@ A boolean specifying whether the secret must be supplied.
 
 ## `env`
 
-A `map` of environment variables that are available to the steps of all jobs in the workflow. You can also set environment variables that are only available to the steps of a single job or to a single step. For more information, see [`jobs.<job_id>.env`](#jobsjob_idenv) and [`jobs.<job_id>.steps[*].env`](#jobsjob_idstepsenv).
+A `map` of environment variables that are available to the steps of all jobs in the workflow. You can also set environment variables that are only available to the steps of a single job or to a single step. For more information, see [`jobs.<job_id>.env`](#jobsjob_idenv) and [`jobs.<job_id>.steps[*].env`](#jobsjob_idstepsenv). 
+
+Variables in the `env` map cannot be defined in terms of other variables in the map.
 
 {% data reusables.repositories.actions-env-var-note %}