submodule: add failing test for option-injection protection in url and path

tests/submodule/inject_option.c

+#include "clar_libgit2.h"
+#include "posix.h"
+#include "path.h"
+#include "submodule_helpers.h"
+#include "fileops.h"
+#include "repository.h"
+
+static git_repository *g_repo = NULL;
+
+void test_submodule_inject_option__initialize(void)
+{
+	g_repo = setup_fixture_submodule_simple();
+}
+
+void test_submodule_inject_option__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+}
+
+static int find_naughty(git_submodule *sm, const char *name, void *payload)
+{
+	int *foundit = (int *) payload;
+
+	GIT_UNUSED(sm);
+
+	if (!git__strcmp("naughty", name))
+		*foundit = true;
+
+	return 0;
+}
+
+void test_submodule_inject_option__url(void)
+{
+	int foundit;
+	git_submodule *sm;
+	git_buf buf = GIT_BUF_INIT;
+
+	cl_git_pass(git_buf_joinpath(&buf, git_repository_workdir(g_repo), ".gitmodules"));
+	cl_git_rewritefile(buf.ptr,
+			   "[submodule \"naughty\"]\n"
+			   "    path = testrepo\n"
+			   "    url = -u./payload\n");
+	git_buf_dispose(&buf);
+
+	/* We do want to find it, but with the appropriate field empty */
+	foundit = 0;
+	cl_git_pass(git_submodule_foreach(g_repo, find_naughty, &foundit));
+	cl_assert_equal_i(1, foundit);
+
+	cl_git_pass(git_submodule_lookup(&sm, g_repo, "naughty"));
+	cl_assert_equal_s("testrepo", git_submodule_path(sm));
+	cl_assert_equal_p(NULL, git_submodule_url(sm));
+
+	git_submodule_free(sm);
+}
+
+void test_submodule_inject_option__path(void)
+{
+	int foundit;
+	git_submodule *sm;
+	git_buf buf = GIT_BUF_INIT;
+
+	cl_git_pass(git_buf_joinpath(&buf, git_repository_workdir(g_repo), ".gitmodules"));
+	cl_git_rewritefile(buf.ptr,
+			   "[submodule \"naughty\"]\n"
+			   "    path = --something\n"
+			   "    url = blah.git\n");
+	git_buf_dispose(&buf);
+
+	/* We do want to find it, but with the appropriate field empty */
+	foundit = 0;
+	cl_git_pass(git_submodule_foreach(g_repo, find_naughty, &foundit));
+	cl_assert_equal_i(1, foundit);
+
+	cl_git_pass(git_submodule_lookup(&sm, g_repo, "naughty"));
+	cl_assert_equal_s("naughty", git_submodule_path(sm));
+	cl_assert_equal_s("blah.git", git_submodule_url(sm));
+
+	git_submodule_free(sm);
+}