{cvs,svn}import: use the new 'git read-tree --empty'

Since fb1bb96 (read-tree: deprecate syntax without tree-ish args,
2010-09-10) not passing --empty caused a spurious warning that was
shown to the user.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/examples/git-svnimport.perl

@@ -289,7 +289,7 @@ my $current_rev = $opt_s || 1;
 unless(-d $git_dir) {
 	system("git init");
 	die "Cannot init the GIT db at $git_tree: $?\n" if $?;
-	system("git read-tree");
+	system("git read-tree --empty");
 	die "Cannot init an empty tree: $?\n" if $?;
 
 	$last_branch = $opt_o;

git-cvsimport.perl

@@ -611,7 +611,7 @@ my %index; # holds filenames of one index per branch
 unless (-d $git_dir) {
 	system(qw(git init));
 	die "Cannot init the GIT db at $git_tree: $?\n" if $?;
-	system(qw(git read-tree));
+	system(qw(git read-tree --empty));
 	die "Cannot init an empty tree: $?\n" if $?;
 
 	$last_branch = $opt_o;