diff returns exit(1) if there are any differences [fixes #243]

ci/release_notes.md

@@ -0,0 +1 @@
+* `spruce diff` now returns exit status 1 if there are any differences; and exit status 0 if no differences [thanks @drnic]

cmd/spruce/main.go

@@ -168,13 +168,16 @@ func main() {
 			usage()
 			return
 		}
-		output, err := diffFiles(options.Diff.Files)
+		output, differences, err := diffFiles(options.Diff.Files)
 		if err != nil {
 			PrintfStdErr("%s\n", err)
 			exit(2)
 			return
 		}
 		printfStdOut("%s\n", output)
+		if differences {
+			exit(1)
+		}
 
 	default:
 		usage()
@@ -342,38 +345,38 @@ func dequoteConcourse(input []byte) string {
 	return re.ReplaceAllString(string(input), "$1")
 }
 
-func diffFiles(paths []string) (string, error) {
+func diffFiles(paths []string) (string, bool, error) {
 	if len(paths) != 2 {
-		return "", ansi.Errorf("incorrect number of files given to diffFiles(); please file a bug report")
+		return "", false, ansi.Errorf("incorrect number of files given to diffFiles(); please file a bug report")
 	}
 
 	data, err := ioutil.ReadFile(paths[0])
 	if err != nil {
-		return "", ansi.Errorf("@R{Error reading file} @m{%s}: %s\n", paths[0], err)
+		return "", false, ansi.Errorf("@R{Error reading file} @m{%s}: %s\n", paths[0], err)
 	}
 	a, err := parseYAML(data)
 	if err != nil {
-		return "", ansi.Errorf("@m{%s}: @R{%s}\n", paths[0], err)
+		return "", false, ansi.Errorf("@m{%s}: @R{%s}\n", paths[0], err)
 	}
 
 	data, err = ioutil.ReadFile(paths[1])
 	if err != nil {
-		return "", ansi.Errorf("@R{Error reading file} @m{%s}: %s\n", paths[1], err)
+		return "", false, ansi.Errorf("@R{Error reading file} @m{%s}: %s\n", paths[1], err)
 	}
 	b, err := parseYAML(data)
 	if err != nil {
-		return "", ansi.Errorf("@m{%s}: @R{%s}\n", paths[1], err)
+		return "", false, ansi.Errorf("@m{%s}: @R{%s}\n", paths[1], err)
 	}
 
 	d, err := Diff(a, b)
 	if err != nil {
-		return "", ansi.Errorf("@R{Failed to diff} @m{%s} -> @m{%s}: %s\n", paths[0], paths[1], err)
+		return "", false, ansi.Errorf("@R{Failed to diff} @m{%s} -> @m{%s}: %s\n", paths[0], paths[1], err)
 	}
 
 	if !d.Changed() {
-		return ansi.Sprintf("@G{both files are semantically equivalent; no differences found!}\n"), nil
+		return ansi.Sprintf("@G{both files are semantically equivalent; no differences found!}\n"), false, nil
 	}
-	return d.String("$"), nil
+	return d.String("$"), true, nil
 }
 
 type RootIsArrayError struct {