parsers: rewrite index_ancestors() in terms of index_commonancestorsheads() The first 80% of index_ancestors() is identical to index_commonancestorsheads(), so just call that function instead.

filelog: remove unused _file method

histedit: store full node hash in rules Previously histedit only stored the short version of the rule nodes in the state. This meant that later we couldn't resolve a rule node to its full form if the commit had been deleted from the repo. Let's store the full form from the beginning.