Environment variable overrides (#74)

* Environment variable overrides

* Remove ORCHARD_CONTEXT

README.md

@@ -66,3 +66,13 @@ From architecture perspective, Orchard has a lower level API for port forwarding
 All port forwarding connections are done via the Orchard Controller instance which "proxies" a secure connection to the Orchard Workers.
 Therefore, your workers can be located under a stricter firewall that only allows connections to the Orchard Controller instance.
 Orchard Controller instance is secured by default and all API calls are authenticated and authorized.
+
+### Environment variables
+
+In addition to controlling the Orchard via the CLI arguments, there are environment variables that may be beneficial both when automating Orchard and in daily use:
+
+| Variable name                   | Description                                                                        |
+|---------------------------------|------------------------------------------------------------------------------------|
+| `ORCHARD_URL`                   | Override controller URL on per-command basis                                       |
+| `ORCHARD_SERVICE_ACCOUNT_NAME`  | Override service account name (used for controller API auth) on per-command basis  |
+| `ORCHARD_SERVICE_ACCOUNT_TOKEN` | Override service account token (used for controller API auth) on per-command basis |

internal/config/env.go

@@ -0,0 +1,7 @@
+package config
+
+const (
+	OrchardURL                 = "ORCHARD_URL"
+	OrchardServiceAccountName  = "ORCHARD_SERVICE_ACCOUNT_NAME"
+	OrchardServiceAccountToken = "ORCHARD_SERVICE_ACCOUNT_TOKEN"
+)

internal/config/handle.go

@@ -116,6 +116,17 @@ func (handle *Handle) DefaultContext() (Context, error) {
 		}
 	}
 
+	// Environment variable overrides
+	if url, ok := os.LookupEnv(OrchardURL); ok {
+		defaultContext.URL = url
+	}
+	if serviceAccountName, ok := os.LookupEnv(OrchardServiceAccountName); ok {
+		defaultContext.ServiceAccountName = serviceAccountName
+	}
+	if serviceAccountToken, ok := os.LookupEnv(OrchardServiceAccountToken); ok {
+		defaultContext.ServiceAccountToken = serviceAccountToken
+	}
+
 	return defaultContext, nil
 }