blameview: Use git-cat-file to read the file content.

Fix blameview to use git-cat-file to read the file content.
This make sure we show the right content when we have modified
file in the working directory which is not committed.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

contrib/blameview/blameview.perl

@@ -28,7 +28,8 @@ $fileview->get_column(0)->set_spacing(0);
 $fileview->set_size_request(1024, 768);
 $fileview->set_rules_hint(1);
 
-open(my $fh, '<', $fn)
+my $fh;
+open($fh, '-|', "git cat-file blob HEAD:$fn")
   or die "unable to open $fn: $!";
 while(<$fh>) {
   chomp;