main: Add ZSH_HIGHLIGHT_DIRS_BLACKLIST

Closes zsh-users#379.

Author: phy1729

highlighters/main/main-highlighter.zsh

@@ -756,14 +756,27 @@ _zsh_highlight_main_highlighter_highlight_path_separators()
 _zsh_highlight_main_highlighter_check_path()
 {
   _zsh_highlight_main_highlighter_expand_path $arg;
-  local expanded_path="$REPLY"
+  local expanded_path="$REPLY" tmp_path
 
   REPLY=path
 
   [[ -z $expanded_path ]] && return 1
   [[ -L $expanded_path ]] && return 0
   [[ -e $expanded_path ]] && return 0
 
+  # Check if this is a disallowed path
+  if [[ $expanded_path[1] == / ]]; then
+    tmp_path=$expanded_path
+  else
+    tmp_path=$PWD/$expanded_path
+  fi
+  tmp_path=$tmp_path:a
+
+  while [[ $tmp_path != / ]]; do
+    [[ -z "${tmp_path:|ZSH_HIGHLIGHT_DIRS_BLACKLIST}" ]] &&  return 1
+    tmp_path=$tmp_path:h
+  done
+
   # Search the path in CDPATH
   local cdpath_dir
   for cdpath_dir in $cdpath ; do
@@ -1063,3 +1076,4 @@ else
   # Make sure the cache is unset
   unset _zsh_highlight_main__command_type_cache
 fi
+typeset -ga ZSH_HIGHLIGHT_DIRS_BLACKLIST