tree-diff: allow diff_tree_sha1 to accept NULL sha1

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 <kirr@mns.spb.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/tree-diff.c b/tree-diff.c
index 456660c7a29ef75030141721205f34134daea51c..b919983e96c4104d7a0667cbd009fe6d052d894b 100644 (file)
--- 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);