hgweb: ensure isdirectory is None for repositories, replacing any True value

Until now, repositories did not provide any value for isdirectory in rows
produced for the index output, and thus isdirectory was generally evaluated as
None for each index entry representing a repository.

However, directories (visible when viewed with the descend and collapse
settings enabled) did provide a value of True and this value appeared to
persist in subsequent rows processed by the templater, causing isdirectory
tests in templates to produce incorrect results for index entries appearing
after directories.

This patch asserts the None value for repositories, thus erasing any such
persistent True values.

mercurial/hgweb/hgwebdir_mod.py

@@ -365,7 +365,8 b' class hgwebdir(object):'
                            description_sort=description.upper() or "unknown",
                            lastchange=d,
                            lastchange_sort=d[1]-d[0],
-                           archives=archivelist(u, "tip", url))
+                           archives=archivelist(u, "tip", url),
+                           isdirectory=None)
 
                 seenrepos.add(name)
                 yield row