run: reject .ww directories as named sources

cmd/ww/main.c

@@ -7706,6 +7706,19 @@ do_run(int argc, char **argv)
 	if (src == NULL) src = ".";
 	struct stat requested;
 	int literal = stat(src, &requested) == 0;
+	if (literal && S_ISDIR(requested.st_mode)) {
+		size_t n = strlen(src);
+		if (n >= 3 && strcmp(src + n - 3, ".ww") == 0) {
+			if (n >= 8 && strcmp(src + n - 8, "_test.ww") == 0)
+				fprintf(stderr,
+				    "ww: cannot run *_test.ww files (%s)\n", src);
+			else
+				fprintf(stderr,
+				    "%s is a directory, should be a WW file\n", src);
+			free(incs);
+			return 1;
+		}
+	}
 	char resolved[PATH_MAX];
 	int is_dir = 0;
 	if (!resolve_module(src, incs, resolved, sizeof resolved, &is_dir)) {