Merge branch 'maximchick-master'

Author: inconshreveable

apply.go

@@ -112,6 +112,7 @@ func Apply(update io.Reader, opts Options) error {
 		return err
 	}
 	defer fp.Close()
+
 	_, err = io.Copy(fp, bytes.NewReader(newBytes))
 	if err != nil {
 		return err
@@ -122,7 +123,11 @@ func Apply(update io.Reader, opts Options) error {
 	fp.Close()
 
 	// this is where we'll move the executable to so that we can swap in the updated replacement
-	oldPath := filepath.Join(updateDir, fmt.Sprintf(".%s.old", filename))
+	oldPath := opts.OldSavePath
+	removeOld := opts.OldSavePath == ""
+	if removeOld {
+		oldPath = filepath.Join(updateDir, fmt.Sprintf(".%s.old", filename))
+	}
 
 	// delete any existing old exec file - this is necessary on Windows for two reasons:
 	// 1. after a successful update, Windows can't remove the .old file because the process is still running
@@ -154,12 +159,14 @@ func Apply(update io.Reader, opts Options) error {
 		return err
 	}
 
-	// move successful, remove the old binary
-	errRemove := os.Remove(oldPath)
+	// move successful, remove the old binary if needed
+	if removeOld {
+		errRemove := os.Remove(oldPath)
 
-	// windows has trouble with removing old binaries, so hide it instead
-	if errRemove != nil {
-		_ = hideFile(oldPath)
+		// windows has trouble with removing old binaries, so hide it instead
+		if errRemove != nil {
+			_ = hideFile(oldPath)
+		}
 	}
 
 	return nil
@@ -212,6 +219,10 @@ type Options struct {
 	// If nil, treat the update as a complete replacement for the contents of the file at TargetPath.
 	// If non-nil, treat the update contents as a patch and use this object to apply the patch.
 	Patcher Patcher
+
+	// Store the old executable file at this path after a successful update.
+	// The empty string means the old executable file will be removed after the update.
+	OldSavePath string
 }
 
 // CheckPermissions determines whether the process has the correct permissions to

apply_test.go

@@ -61,6 +61,28 @@ func TestApplySimple(t *testing.T) {
 	validateUpdate(fName, err, t)
 }
 
+func TestApplyOldSavePath(t *testing.T) {
+	t.Parallel()
+
+	fName := "TestApplyOldSavePath"
+	defer cleanup(fName)
+	writeOldFile(fName, t)
+
+	oldfName := "OldSavePath"
+
+	err := Apply(bytes.NewReader(newFile), Options{
+		TargetPath:  fName,
+		OldSavePath: oldfName,
+	})
+	validateUpdate(fName, err, t)
+
+	if _, err := os.Stat(oldfName); os.IsNotExist(err) {
+		t.Fatalf("Failed to find the old file: %v", err)
+	}
+
+	cleanup(oldfName)
+}
+
 func TestVerifyChecksum(t *testing.T) {
 	t.Parallel()