fix(gitFs): force renovate.json add

lib/platform/git/storage.js

@@ -291,7 +291,12 @@ class Storage {
         for (const file of files) {
           await fs.writeFile(join(cwd, file.name), Buffer.from(file.contents));
         }
-        await git.add(files.map(f => f.name));
+        const fileNames = files.map(f => f.name);
+        // istanbul ignore if
+        if (fileNames.length === 1 && fileNames[0] === 'renovate.json') {
+          fileNames.shift('-f');
+        }
+        await git.add(fileNames);
         await git.commit(message);
         await git.push([
           'origin',