tree-diff: allow diff_tree_sha1 to accept NULL sha1

Kirill Smelkov · gitster · commit 791303284cb3 · 2014-02-05T10:48:14.000-08:00
which would mean that corresponding tree - old or new - is empty.

As followup patches will show, that functionality was already needed in
several places of Git codebase, but there, we were preparing empty
tree_desc objects by hand, with some code duplication.

For handling sha1 = NULL case, let's reuse fill_tree_descriptor() which
returns just empty tree_desc in that case.

Signed-off-by: Kirill Smelkov &lt;kirr@mns.spb.ru&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/tree-diff.c b/tree-diff.c
@@ -294,14 +294,10 @@ int diff_tree_sha1(const unsigned char *old, const unsigned char *new, const cha
 	unsigned long size1, size2;
 	int retval;
 
-	tree1 = read_object_with_reference(old, tree_type, &size1, NULL);
-	if (!tree1)
-		die("unable to read source tree (%s)", sha1_to_hex(old));
-	tree2 = read_object_with_reference(new, tree_type, &size2, NULL);
-	if (!tree2)
-		die("unable to read destination tree (%s)", sha1_to_hex(new));
-	init_tree_desc(&t1, tree1, size1);
-	init_tree_desc(&t2, tree2, size2);
+	tree1 = fill_tree_descriptor(&t1, old);
+	tree2 = fill_tree_descriptor(&t2, new);
+	size1 = t1.size;
+	size2 = t2.size;
 	retval = diff_tree(&t1, &t2, base, opt);
 	if (!*base && DIFF_OPT_TST(opt, FOLLOW_RENAMES) && diff_might_be_rename()) {
 		init_tree_desc(&t1, tree1, size1);
