localrepo: use "vfs.islink()" instead of "os.path.islink()"

mercurial/localrepo.py

@@ -735,7 +735,7 b' class localrepository(object):'
         return self.wopener(f, mode)
 
     def _link(self, f):
-        return os.path.islink(self.wjoin(f))
+        return self.wvfs.islink(f)
 
     def _loadfilter(self, filter):
         if filter not in self.filterpats:

mercurial/scmutil.py

@@ -242,6 +242,9 b' class abstractvfs(object):'
     def isdir(self, path=None):
         return os.path.isdir(self.join(path))
 
+    def islink(self, path=None):
+        return os.path.islink(self.join(path))
+
     def makedir(self, path=None, notindexed=True):
         return util.makedir(self.join(path), notindexed)