ignore: enhance git_ignore_path_is_ignored() test coverage

tests-clar/attr/ignore.c

+#include "clar_libgit2.h"
+
+static git_repository *g_repo = NULL;
+
+void test_attr_ignore__initialize(void)
+{
+    g_repo = cl_git_sandbox_init("attr");
+}
+
+void test_attr_ignore__cleanup(void)
+{
+    cl_git_sandbox_cleanup();
+    g_repo = NULL;
+}
+
+void assert_is_ignored(bool expected, const char *filepath)
+{
+    int is_ignored;
+
+    cl_git_pass(git_ignore_path_is_ignored(&is_ignored, g_repo, filepath));
+    cl_assert_equal_i(expected, is_ignored == 1);
+}
+
+void test_attr_ignore__honor_temporary_rules(void)
+{
+    cl_git_rewritefile("attr/.gitignore", "/NewFolder\n/NewFolder/NewFolder");
+
+    assert_is_ignored(false, "File.txt");
+    assert_is_ignored(true, "NewFolder");
+    assert_is_ignored(true, "NewFolder/NewFolder");
+    assert_is_ignored(true, "NewFolder/NewFolder/File.txt");
+}