Add a convenience constructeur to SGPath

simgear/misc/sg_path.cxx

@@ -86,6 +86,15 @@ SGPath::SGPath( const std::string& p )
     fix();
 }
 
+// create a path based on "path" and a "subpath"
+SGPath::SGPath( const SGPath& p, const std::string& r )
+    : path(p.path),
+    _cached(false)
+{
+    append(r);
+    fix();
+}
+
 SGPath::SGPath(const SGPath& p) :
   path(p.path),
   _cached(p._cached),

simgear/misc/sg_path.hxx

@@ -58,6 +58,7 @@ public:
     /** Default constructor */
     SGPath();
 
+    /** Copy contructor */
     SGPath(const SGPath& p);
     
     SGPath& operator=(const SGPath& p);
@@ -68,6 +69,13 @@ public:
      */
     SGPath( const std::string& p );
 
+    /**
+     * Construct a path based on the starting path provided and a relative subpath
+     * @param p initial path
+     * @param r relative subpath
+     */
+    SGPath( const SGPath& p, const std::string& r );
+
     /** Destructor */
     ~SGPath();