Fix rename detection for tree-to-tree diffs

The performance improvements I introduced for rename detection
were not able to run successfully for tree-to-tree diffs because
the blob size was not known early enough and so the file signature
always had to be calculated nonetheless.

This change separates loading blobs into memory from calculating
the signature.  I can't avoid having to load the large blobs into
memory, but by moving it forward, I'm able to avoid the signature
calculation if the blob won't come into play for renames.

1 files changed, 48 insertions, 2 deletions

diff --git a/tests-clar/diff/rename.c b/tests-clar/diff/rename.c
index ed58b7aa9..79c89e362 100644
--- a/tests-clar/diff/rename.c
+++ b/tests-clar/diff/rename.c
@@ -1126,7 +1126,7 @@ void test_diff_rename__unmodified_can_be_renamed(void)
 void test_diff_rename__many_files(void)
 {
 	git_index *index;
-	git_tree *tree;
+	git_tree *tree, *new_tree;
 	git_diff_list *diff = NULL;
 	diff_expects exp;
 	git_diff_options diffopts = GIT_DIFF_OPTIONS_INIT;
@@ -1176,6 +1176,52 @@ void test_diff_rename__many_files(void)
 	cl_assert_equal_i(51, exp.files);
 
 	git_diff_list_free(diff);
-	git_index_free(index);
+
+	{
+		git_object *parent;
+		git_signature *sig;
+		git_oid tree_id, commit_id;
+		git_reference *ref;
+
+		cl_git_pass(git_index_write_tree(&tree_id, index));
+		cl_git_pass(git_tree_lookup(&new_tree, g_repo, &tree_id));
+
+		cl_git_pass(git_revparse_ext(&parent, &ref, g_repo, "HEAD"));
+		cl_git_pass(git_signature_new(
+			&sig, "Sm Test", "sm@tester.test", 1372350000, 480));
+
+		cl_git_pass(git_commit_create_v(
+			&commit_id, g_repo, git_reference_name(ref), sig, sig,
+			NULL, "yoyoyo", new_tree, 1, parent));
+
+		git_object_free(parent);
+		git_reference_free(ref);
+		git_signature_free(sig);
+	}
+
+	cl_git_pass(git_diff_tree_to_tree(
+		&diff, g_repo, tree, new_tree, &diffopts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, NULL, NULL, &exp));
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_DELETED]);
+	cl_assert_equal_i(51, exp.file_status[GIT_DELTA_ADDED]);
+	cl_assert_equal_i(52, exp.files);
+
+	opts.flags = GIT_DIFF_FIND_ALL;
+	cl_git_pass(git_diff_find_similar(diff, &opts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, NULL, NULL, &exp));
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_RENAMED]);
+	cl_assert_equal_i(50, exp.file_status[GIT_DELTA_ADDED]);
+	cl_assert_equal_i(51, exp.files);
+
+	git_diff_list_free(diff);
+
+	git_tree_free(new_tree);
 	git_tree_free(tree);
+	git_index_free(index);
 }