builder/digitalocean: use detected env variables for credentials

builder/digitalocean/builder.go

@@ -12,6 +12,7 @@ import (
 	"github.com/mitchellh/packer/builder/common"
 	"github.com/mitchellh/packer/packer"
 	"log"
+	"os"
 	"strconv"
 	"text/template"
 	"time"
@@ -64,6 +65,16 @@ func (b *Builder) Prepare(raws ...interface{}) error {
 
 	// Optional configuration with defaults
 	//
+	if b.config.APIKey == "" {
+		// Default to environment variable for api_key, if it exists
+		b.config.APIKey = os.Getenv("DIGITALOCEAN_API_KEY")
+	}
+
+	if b.config.ClientID == "" {
+		// Default to environment variable for client_id, if it exists
+		b.config.ClientID = os.Getenv("DIGITALOCEAN_CLIENT_ID")
+	}
+
 	if b.config.RegionID == 0 {
 		// Default to Region "New York"
 		b.config.RegionID = 1

website/source/docs/builders/digitalocean.html.markdown

@@ -25,11 +25,13 @@ Required:
 
 * `api_key` (string) - The API key to use to access your account. You can
   retrieve this on the "API" page visible after logging into your account
-  on DigitalOcean.
+  on DigitalOcean. Alternatively, the builder looks for the environment
+  variable `DIGITALOCEAN_API_KEY`.
 
 * `client_id` (string) - The client ID to use to access your account. You can
   find this on the "API" page visible after logging into your account on
-  DigitalOcean.
+  DigitalOcean. Alternatively, the builder looks for the environment
+  variable `DIGITALOCEAN_CLIENT_ID`.
 
 Optional: