hgweb: introduction a filerevnav subclass

It'll be use to implement the file specific behavior.

mercurial/hgweb/webcommands.py

@@ -772,7 +772,7 b' def filelog(web, req, tmpl):'
             yield e
 
     nodefunc = lambda x: fctx.filectx(fileid=x)
-    nav = webutil.revnav(nodefunc).gen(end - 1, revcount, count)
+    nav = webutil.filerevnav(nodefunc).gen(end - 1, revcount, count)
     return tmpl("filelog", file=f, node=fctx.hex(), nav=nav,
                 entries=lambda **x: entries(latestonly=False, **x),
                 latestentry=lambda **x: entries(latestonly=True, **x),

mercurial/hgweb/webutil.py

@@ -93,6 +93,9 b' class revnav(object):'
         return ({'before': lambda **map: (data(i) for i in navbefore),
                  'after':  lambda **map: (data(i) for i in navafter)},)
 
+class filerevnav(revnav):
+    pass
+
 def _siblings(siblings=[], hiderev=None):
     siblings = [s for s in siblings if s.node() != nullid]
     if len(siblings) == 1 and siblings[0].rev() == hiderev: