Add sub folders as input sources

gpx2html/__init__.py

@@ -124,9 +124,10 @@ class Gpx2Html(object):
         self.update()
 
     def update(self):
-        infiles = glob.glob(os.path.join(self.infolder, '*.gpx'))
-        for filename in infiles:
-            self.tracks.add(filename)
+        for root, _, files in os.walk(self.infolder):
+            for name in files:
+                if name.endswith(".gpx"):
+                    self.tracks.add(os.path.join(root, name))
 
         self.logger.info("Begin update of png's/html...")
         distances = list()