layouts: pull tag location list management into layout module We keep a list of locations within subversion where we look for tags that persists across runs. This pulls the logic for constructiong that list from config on first clone, and for mainting the list afterwards out of svnmeta and into layouts.

include Makefile hgsubversion/help/*.rst tests/fixtures/invalid_utf8.tar.gz
recursive-include tests *.py *.sh *.svndump *.txt