windows: call DeleteFileW and RemoveDirectoryW to be able to remove s…

…ymlinks before restore

Windows symlinks could not be replaced during restore because
win32_unlink() only used _wunlink() to remove existing files before
recovery. _wunlink() cannot remove symlinks so that the
overwrite of existing symlinks did not work.

We first try with _unlink(); on failure DeleteFileW()
and as last option we do RemoveDirectoryW()

win32_unlink now is able to remove:
 * direcories
 * files
 * file symlinks and
 * directory symlinks

Fixes #967: Symbolic links are not replaceable during restore on Win FD

src/win32/compat/compat.c

@@ -2873,7 +2873,34 @@ int win32_unlink(const char *filename)
             }
          }
       }
+
+      /* if deletion with _unlink failed, try to use DeleteFileW (which also can remove file links) */
+      if (nRetCode == -1) {
+         Dmsg0(100, "_unlink failed, trying DeleteFileW \n");
+         if (DeleteFileW( (LPCWSTR)pwszBuf ) == 0) { // 0 = fail
+            Dmsg0(100, "DeleteFileW failed\n");
+            nRetCode = -1;
+         } else {
+            Dmsg0(100, "DeleteFileW success\n");
+            nRetCode = 0;
+         }
+      }
+
+
+      /* if deletion with DeleteFileW failed, try to use RemoveDirectoryW (which also can remove directory links) */
+      if (nRetCode == -1) {
+         Dmsg0(100, "DeleteFileW failed, trying RemoveDirectoryW \n");
+         if (RemoveDirectoryW( (LPCWSTR)pwszBuf ) == 0) { // 0 = fail
+            Dmsg0(100, "RemoveDirectoryW failed\n");
+            nRetCode = -1;
+         } else {
+            Dmsg0(100, "RemoveDirectoryW success\n");
+            nRetCode = 0;
+         }
+      }
+
       free_pool_memory(pwszBuf);
+
    } else {
       nRetCode = _unlink(filename);