add tree_isvalid() function

src/lib66/tree_isvalid.c

+/*
+ * tree_isvalid.c
+ *
+ * Copyright (c) 2018-2021 Eric Vidal <eric@obarun.org>
+ *
+ * All rights reserved.
+ *
+ * This file is part of Obarun. It is subject to the license terms in
+ * the LICENSE file found in the top-level directory of this
+ * distribution.
+ * This file may not be copied, modified, propagated, or distributed
+ * except according to the terms contained in the LICENSE file./
+ */
+
+#include <66/tree.h>
+
+#include <sys/types.h>
+
+#include <oblibs/types.h>
+#include <oblibs/string.h>
+
+#include <66/constants.h>
+#include <66/ssexec.h>
+
+int tree_isvalid(ssexec_t *info)
+{
+    int r ;
+
+    char treename[info->base.len + SS_SYSTEM_LEN + 1 + info->treename.len + 1] ;
+    auto_strings(treename, info->base.s, SS_SYSTEM, "/", info->treename.s) ;
+
+    r = scan_mode(treename, S_IFDIR) ;
+    if (r < 0)
+        return -1 ;
+    else if (!r)
+        return 0 ;
+
+    return 1 ;
+}