Add wxDIR_NO_FOLLOW flag for wxDir iteration.

This flag allows to avoid following the symbolic links during the directory
traversal. In particular, this means that links to the directories
(potentially outside the directory being traversed) are not considered as
directories at all when it is used, potentially avoiding surprises.

Closes #14542.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72740 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/dir.h

@@ -94,8 +94,8 @@ public:
 
 
 /**
-    These flags define what kind of filenames are included in the list of files
-    enumerated by wxDir::GetFirst() and wxDir::GetNext().
+    These flags affect the behaviour of GetFirst/GetNext() and Traverse(),
+    determining what types are included in the list of items they produce.
 */
 enum wxDirFlags
 {
@@ -104,8 +104,28 @@ enum wxDirFlags
     wxDIR_HIDDEN    = 0x0004,   ///< Includes hidden files.
     wxDIR_DOTDOT    = 0x0008,   ///< Includes "." and "..".
 
-    //! Combination of the @c wxDIR_FILES, @c wxDIR_DIRS, @c wxDIR_HIDDEN flags
-    //! defined above.
+    /**
+        Don't follow symbolic links during the directory traversal.
+
+        This flag is ignored under systems not supporting symbolic links (i.e.
+        non-Unix ones).
+
+        Notice that this flag is @e not included in wxDIR_DEFAULT and so the
+        default behaviour of wxDir::Traverse() is to follow symbolic links,
+        even if they lead outside of the directory being traversed.
+
+        @since 2.9.5
+     */
+    wxDIR_NO_FOLLOW = 0x0010,
+
+    /**
+        Default directory traversal flags include both files and directories,
+        even hidden.
+
+        Notice that by default wxDIR_NO_FOLLOW is @e not included, meaning that
+        symbolic links are followed by default. If this is not desired, you
+        must pass that flag explicitly.
+     */
     wxDIR_DEFAULT   = wxDIR_FILES | wxDIR_DIRS | wxDIR_HIDDEN
 };