git-cvsimport: force checkout of working tree after initial import

When creating a brand new git repository through git-cvsimport (not
incremental import), force a checkout of HEAD of master as working tree
after successful import using the -f switch to git checkout.  Otherwise
the working tree is empty, and all files are reported as 'deleted' by
git status.

This was noticed and reported by Cameron Dale through
 http://bugs.debian.org/430903Signed-off-by: NGerrit Pape <pape@smarden.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

git-cvsimport.perl

@@ -1007,7 +1007,7 @@ sub commit {
 		if ($opt_r && $opt_o ne 'HEAD');
 	system('git-update-ref', 'HEAD', "$orig_branch");
 	unless ($opt_i) {
-		system('git checkout');
+		system('git checkout -f');
 		die "checkout failed: $?\n" if $?;
 	}
 }