Add Markdown and ZIP notebook import

internal/vault/vault.go

@@ -696,12 +696,7 @@ func (v *Vault) SaveAsset(note, origName string, r io.Reader, limit int64) (stri
 	if int64(len(data)) > limit {
 		return "", ErrTooLarge
 	}
-	ext := strings.ToLower(filepath.Ext(origName))
-	if !extPattern.MatchString(ext) {
-		ext = sniffExt(data)
-	}
-	sum := sha256.Sum256(data)
-	name := hex.EncodeToString(sum[:8]) + ext
+	name := assetName(data, origName)
 	dir := AssetsDir(p)
 	v.mu.Lock()
 	defer v.mu.Unlock()
@@ -722,6 +717,15 @@ func (v *Vault) SaveAsset(note, origName string, r io.Reader, limit int64) (stri
 	return EscapeLinkPath(path.Base(AssetsDir(note))) + "/" + name, nil
 }
 
+func assetName(data []byte, origName string) string {
+	ext := strings.ToLower(filepath.Ext(origName))
+	if !extPattern.MatchString(ext) {
+		ext = sniffExt(data)
+	}
+	sum := sha256.Sum256(data)
+	return hex.EncodeToString(sum[:8]) + ext
+}
+
 func sniffExt(data []byte) string {
 	switch http.DetectContentType(data) {
 	case "image/png":