git-gui: show the maxrecentrepo config option in the preferences dialog

Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>
diff --git a/git-gui.sh b/git-gui.sh
index 153f85d..4a6929e 100755
--- a/git-gui.sh
+++ b/git-gui.sh
@@ -894,6 +894,7 @@
 set default_config(gui.pruneduringfetch) false
 set default_config(gui.trustmtime) false
 set default_config(gui.fastcopyblame) false
+set default_config(gui.maxrecentrepo) 10
 set default_config(gui.copyblamethreshold) 40
 set default_config(gui.blamehistoryctx) 7
 set default_config(gui.diffcontext) 5