feat(cmd): refresh-units accepts -t for tag, branch, or SHA

cmd/cmd.go

@@ -1,6 +1,7 @@
 package cmd
 
 import (
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"net/http"
@@ -277,10 +278,12 @@ deisctl looks for unit files in these directories, in this order:
 - /var/lib/deis/units
 
 Usage:
-  deisctl refresh-units [-p <target>]
+  deisctl refresh-units [-p <target>] [-t <tag>]
 
 Options:
   -p --path=<target>   where to save unit files [default: /var/lib/deis/units]
+  -t --tag=<tag>       git tag, branch, or SHA to use when downloading unit files
+                       [default: master]
 `
 	// parse command-line arguments
 	args, err := docopt.Parse(usage, nil, true, "", false)
@@ -295,7 +298,7 @@ Options:
 	}
 	// download and save the unit files to the specified path
 	rootURL := "https://raw.githubusercontent.com/deis/deisctl/"
-	branch := "master"
+	tag := args["--tag"].(string)
 	units := []string{
 		"deis-builder.service",
 		"deis-builder-data.service",
@@ -310,12 +313,15 @@ Options:
 		"deis-router.service",
 	}
 	for _, unit := range units {
-		src := rootURL + branch + "/units/" + unit
+		src := rootURL + tag + "/units/" + unit
 		dest := filepath.Join(dir, unit)
 		res, err := http.Get(src)
 		if err != nil {
 			return err
 		}
+		if res.StatusCode != 200 {
+			return errors.New(res.Status)
+		}
 		defer res.Body.Close()
 		data, err := ioutil.ReadAll(res.Body)
 		if err != nil {
@@ -324,7 +330,7 @@ Options:
 		if err = ioutil.WriteFile(dest, data, 0644); err != nil {
 			return err
 		}
-		fmt.Printf("Refreshed %s from %s\n", unit, branch)
+		fmt.Printf("Refreshed %s from %s\n", unit, tag)
 	}
 	return nil
 }