revparse: do not segfault when retrieving the last entry

src/revparse.c

@@ -263,7 +263,7 @@ static int walk_ref_history(git_object **out, git_repository *repo, const char *
 					retcode = revparse_lookup_fully_qualifed_ref(out, repo, git_buf_cstr(&buf));
 				else if (!git_reflog_read(&reflog, disambiguated)) {
 						int numentries = git_reflog_entrycount(reflog);
-						if (numentries < n) {
+						if (numentries < n + 1) {
 							giterr_set(GITERR_REFERENCE, "Reflog for '%s' has only %d entries, asked for %d",
 								git_buf_cstr(&buf), numentries, n);
 							retcode = GIT_ENOTFOUND;

tests-clar/refs/revparse.c

@@ -156,6 +156,7 @@ void test_refs_revparse__ordinal(void)
 	test_object("nope@{0}", NULL);
 	test_object("master@{31415}", NULL);
 	test_object("@{1000}", NULL);
+	test_object("@{2}", NULL);
 
 	test_object("@{0}", "a65fedf39aefe402d3bb6e24df4d4f5fe4547750");
 	test_object("@{1}", "be3563ae3f795b2b4353bcce3a527ad0a4f7f644");