Fix broken revision grid content filter (gitextensions#5450)

* Fix broken revision grid content filter

Previously searching for Foo would run git log with -SFoo (including the quotes).

This commit adds a space and quotes the filter text alone.

* Use -G for git log search over -S

GitUI/UserControls/RevisionGrid/RevisionGridControl.cs

@@ -409,7 +409,7 @@ public void FormatQuickFilter(string filter,
                 {
                     if (cmdLineSafe)
                     {
-                        revListArgs += "\"-S" + filter + "\" ";
+                        revListArgs += "-G" + filter.Quote();
                     }
                     else
                     {