return `null` when .git/config doesn't exist

index.js

@@ -38,7 +38,7 @@ function git(cwd, cb) {
 git.sync = function configSync(cwd) {
   var fp = resolve(cwd);
   if (!fs.existsSync(fp)) {
-    throw new Error('.git/config does not exist.');
+    return null;
   }
   return ini.parse(fs.readFileSync(fp, 'utf8'));
 };

test.js

@@ -17,12 +17,6 @@ describe('sync:', function () {
     git.sync().should.not.have.properties(['foo']);
     git.sync().should.not.throw;
   });
-
-  it('should throw an error when .git/config does not exist:', function () {
-    (function () {
-      git.sync('foo');
-    }).should.throw('.git/config does not exist.');
-  });
 });
 
 describe('async:', function () {