cache: Simplify cache dir creation

internal/cache/cache.go

@@ -85,10 +85,12 @@ func writeCachedirTag(dir string) error {
 // performReadahead returns true.
 func New(id string, basedir string) (c *Cache, err error) {
 	if basedir == "" {
-		basedir, err = defaultCacheDir()
-		if err != nil {
-			return nil, err
-		}
+		basedir, err = DefaultDir()
+	}
+
+	err = mkdirCacheDir(basedir)
+	if err != nil {
+		return nil, err
 	}
 
 	// create base dir and tag it as a cache directory
@@ -108,13 +110,14 @@ func New(id string, basedir string) (c *Cache, err error) {
 		return nil, errors.New("cache version is newer")
 	}
 
-	err = updateTimestamp(cachedir)
-	if err != nil {
+	// create the repo cache dir if it does not exist yet
+	if err = fs.MkdirAll(cachedir, dirMode); err != nil {
 		return nil, err
 	}
 
-	// create the repo cache dir if it does not exist yet
-	if err = fs.MkdirAll(cachedir, dirMode); err != nil {
+	// update the timestamp so that we can detect old cache dirs
+	err = updateTimestamp(cachedir)
+	if err != nil {
 		return nil, err
 	}
 

internal/cache/dir.go

@@ -49,29 +49,25 @@ func darwinCacheDir() (string, error) {
 	return filepath.Join(home, "Library", "Caches", "restic"), nil
 }
 
-// defaultCacheDir determines and creates the default cache directory for this
-// system.
-func defaultCacheDir() (string, error) {
-	var cachedir string
-	var err error
+// DefaultDir returns the default cache directory for the current OS.
+func DefaultDir() (cachedir string, err error) {
 	switch runtime.GOOS {
 	case "darwin":
 		cachedir, err = darwinCacheDir()
 	case "windows":
 		cachedir, err = windowsCacheDir()
-	default:
-		// Default to XDG for Linux and any other OSes.
-		cachedir, err = xdgCacheDir()
-	}
-	if err != nil {
-		return "", err
 	}
 
+	// Default to XDG for Linux and any other OSes.
+	return xdgCacheDir()
+}
+
+func mkdirCacheDir(cachedir string) error {
 	fi, err := fs.Stat(cachedir)
 	if os.IsNotExist(errors.Cause(err)) {
 		err = fs.MkdirAll(cachedir, 0700)
 		if err != nil {
-			return "", errors.Wrap(err, "MkdirAll")
+			return errors.Wrap(err, "MkdirAll")
 		}
 
 		fi, err = fs.Stat(cachedir)
@@ -79,12 +75,12 @@ func defaultCacheDir() (string, error) {
 	}
 
 	if err != nil {
-		return "", errors.Wrap(err, "Stat")
+		return errors.Wrap(err, "Stat")
 	}
 
 	if !fi.IsDir() {
-		return "", errors.Errorf("cache dir %v is not a directory", cachedir)
+		return errors.Errorf("cache dir %v is not a directory", cachedir)
 	}
 
-	return cachedir, nil
+	return nil
 }