odb: only provide the empty tree

Only provide the empty tree internally, which matches git's behavior.
If we provide the empty blob then any users trying to write it with
libgit2 would omit it from actually landing in the odb, which appear
to git proper as a broken repository (missing that object).

src/odb.c

@@ -54,14 +54,9 @@ static int load_alternates(git_odb *odb, const char *objects_dir, int alternate_
 
 static git_otype odb_hardcoded_type(const git_oid *id)
 {
-	static git_oid empty_blob = {{ 0xe6, 0x9d, 0xe2, 0x9b, 0xb2, 0xd1, 0xd6, 0x43, 0x4b, 0x8b,
-					   0x29, 0xae, 0x77, 0x5a, 0xd8, 0xc2, 0xe4, 0x8c, 0x53, 0x91 }};
 	static git_oid empty_tree = {{ 0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60,
 					   0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04 }};
 
-	if (!git_oid_cmp(id, &empty_blob))
-		return GIT_OBJ_BLOB;
-
 	if (!git_oid_cmp(id, &empty_tree))
 		return GIT_OBJ_TREE;
 

tests/odb/emptyobjects.c

@@ -2,29 +2,33 @@
 #include "odb.h"
 #include "filebuf.h"
 
+#define TEST_REPO_PATH "redundant.git"
+
 git_repository *g_repo;
+git_odb *g_odb;
 
 void test_odb_emptyobjects__initialize(void)
 {
-	cl_git_pass(git_repository_open(&g_repo, cl_fixture("testrepo.git")));
+	g_repo = cl_git_sandbox_init(TEST_REPO_PATH);
+	cl_git_pass(git_repository_odb(&g_odb, g_repo));
 }
+
 void test_odb_emptyobjects__cleanup(void)
 {
-	git_repository_free(g_repo);
+	git_odb_free(g_odb);
+	cl_git_sandbox_cleanup();
 }
 
-void test_odb_emptyobjects__read(void)
+void test_odb_emptyobjects__blob_notfound(void)
 {
-	git_oid id;
+	git_oid id, written_id;
 	git_blob *blob;
 
 	cl_git_pass(git_oid_fromstr(&id, "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391"));
-	cl_git_pass(git_blob_lookup(&blob, g_repo, &id));
-	cl_assert_equal_i(GIT_OBJ_BLOB, git_object_type((git_object *) blob));
-	cl_assert(git_blob_rawcontent(blob));
-	cl_assert_equal_s("", git_blob_rawcontent(blob));
-	cl_assert_equal_i(0, git_blob_rawsize(blob));
-	git_blob_free(blob);
+	cl_git_fail_with(GIT_ENOTFOUND, git_blob_lookup(&blob, g_repo, &id));
+
+	cl_git_pass(git_odb_write(&written_id, g_odb, "", 0, GIT_OBJ_BLOB));
+	cl_assert(git_path_exists(TEST_REPO_PATH "/objects/e6/9de29bb2d1d6434b8b29ae775ad8c2e48c5391"));
 }
 
 void test_odb_emptyobjects__read_tree(void)
@@ -43,15 +47,12 @@ void test_odb_emptyobjects__read_tree(void)
 void test_odb_emptyobjects__read_tree_odb(void)
 {
 	git_oid id;
-	git_odb *odb;
 	git_odb_object *tree_odb;
 
 	cl_git_pass(git_oid_fromstr(&id, "4b825dc642cb6eb9a060e54bf8d69288fbee4904"));
-	cl_git_pass(git_repository_odb(&odb, g_repo));
-	cl_git_pass(git_odb_read(&tree_odb, odb, &id));
+	cl_git_pass(git_odb_read(&tree_odb, g_odb, &id));
 	cl_assert(git_odb_object_data(tree_odb));
 	cl_assert_equal_s("", git_odb_object_data(tree_odb));
 	cl_assert_equal_i(0, git_odb_object_size(tree_odb));
 	git_odb_object_free(tree_odb);
-	git_odb_free(odb);
 }