[setup] allow to setup also if target dir is empty

Vault did not allowed to setup storage if target directory had been existed
before. Allow to do it if directory is empty, so directory can be created
separately (e.g. with special permissions, bind mount, symlink etc.)

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>

src/vault.cpp

@@ -337,8 +337,13 @@ void Vault::setup(const QVariantMap *config)
     } else if (config) {
         debug::info("Repository initialization is requested");
 
-        if (os::path::exists(m_path))
-            error::raise({{"msg", "Vault dir already exists, can't create"}, {"path", m_path}});
+        if (os::path::exists(m_path)) {
+            QDir d(m_path);
+            if (!d.entryList(QDir::NoDotAndDotDot).isEmpty())
+                error::raise({
+                        {"msg", "Vault dir already exists and not empty"}
+                        , {"path", m_path}});
+        }
 
         try {
             createRepo();