index: Make _read() cope with index file creation

src/index.c

@@ -461,9 +461,10 @@ int git_index_read(git_index *index)
 		return create_index_error(-1,
 			"Failed to read index: The index is in-memory only");
 
-	if (!index->on_disk || git_path_exists(index->index_file_path) == false) {
+	index->on_disk = git_path_exists(index->index_file_path);
+
+	if (!index->on_disk) {
 		git_index_clear(index);
-		index->on_disk = 0;
 		return 0;
 	}
 

tests-clar/index/tests.c

@@ -484,3 +484,53 @@ void test_index_tests__elocked(void)
 	git_index_free(index);
 	git_repository_free(repo);
 }
+
+void test_index_tests__reload_from_disk(void)
+{
+	git_repository *repo;
+	git_index *read_index;
+	git_index *write_index;
+
+	cl_set_cleanup(&cleanup_myrepo, NULL);
+
+	cl_git_pass(git_futils_mkdir("./myrepo", NULL, 0777, GIT_MKDIR_PATH));
+	cl_git_mkfile("./myrepo/a.txt", "a\n");
+	cl_git_mkfile("./myrepo/b.txt", "b\n");
+
+	cl_git_pass(git_repository_init(&repo, "./myrepo", 0));
+	cl_git_pass(git_repository_index(&write_index, repo));
+	cl_assert_equal_i(false, write_index->on_disk);
+
+	cl_git_pass(git_index_open(&read_index, write_index->index_file_path));
+	cl_assert_equal_i(false, read_index->on_disk);
+
+	/* Stage two new files agaisnt the write_index */
+	cl_git_pass(git_index_add_bypath(write_index, "a.txt"));
+	cl_git_pass(git_index_add_bypath(write_index, "b.txt"));
+
+	cl_assert_equal_sz(2, git_index_entrycount(write_index));
+
+	/* Persist the index changes to disk */
+	cl_git_pass(git_index_write(write_index));
+	cl_assert_equal_i(true, write_index->on_disk);
+
+	/* Sync the changes back into the read_index */
+	cl_assert_equal_sz(0, git_index_entrycount(read_index));
+
+	cl_git_pass(git_index_read(read_index));
+	cl_assert_equal_i(true, read_index->on_disk);
+
+	cl_assert_equal_sz(2, git_index_entrycount(read_index));
+
+	/* Remove the index file from the filesystem */
+	cl_git_pass(p_unlink(write_index->index_file_path));
+
+	/* Sync the changes back into the read_index */
+	cl_git_pass(git_index_read(read_index));
+	cl_assert_equal_i(false, read_index->on_disk);
+	cl_assert_equal_sz(0, git_index_entrycount(read_index));
+
+	git_index_free(read_index);
+	git_index_free(write_index);
+	git_repository_free(repo);
+}