mercurial: enable showfunc diff options to make it similar like git backend.

- fixes  #5614

vcsserver/hg.py

@@ -458,7 +458,7 b' class HgRemote(RemoteBase):'
             match_filter = match(file_filter[0], '', [file_filter[1]])
         else:
             match_filter = file_filter
-        opts = diffopts(git=opt_git, ignorews=opt_ignorews, context=context)
+        opts = diffopts(git=opt_git, ignorews=opt_ignorews, context=context, showfunc=1)
 
         try:
             return "".join(patch.diff(