add--interactive: compute the empty tree value

The interactive add script hard-codes the object ID of the empty tree.
To avoid any problems when changing hashes, compute this value when used
and cache it for any future uses.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-add--interactive.perl b/git-add--interactive.perl
index c1f52e457f6c5b03947766555e10fba33e7e1b38..36f38ced902e1902a626933bdcda09819acf39a7 100755 (executable)
--- a/git-add--interactive.perl
+++ b/git-add--interactive.perl
@@ -205,8 +205,15 @@ my $status_head = sprintf($status_fmt, __('staged'), __('unstaged'), __('path'))
        }
 }
 
-sub get_empty_tree {
-       return '4b825dc642cb6eb9a060e54bf8d69288fbee4904';
+{
+       my $empty_tree;
+       sub get_empty_tree {
+               return $empty_tree if defined $empty_tree;
+
+               $empty_tree = run_cmd_pipe(qw(git hash-object -t tree /dev/null));
+               chomp $empty_tree;
+               return $empty_tree;
+       }
 }
 
 sub get_diff_reference {