convert: keep converted hg parents that are outside convert.hg.revs (BC) Before, when converting revisions without also including their already converted parents in convert.hg.revs, the parents would no longer be parents. That seems unfortunate and we dare to assume that nobody ever wants that. Instead, preserve parents that are outside the current convert range but already have been converted. The parents returned in getcommit() are unconditionally converted, so we introduce a separate optparents with optional parents.

tests: coverage of ancestry with convert in multiple non-overlapping steps This exposes that parent information is lost in cases where it is possible to preserve it - and where it thus would make sense if that was what happened.

revset: rename findaliases() to expandaliases() This function returns a full tree of alias expansion applied, which sounds different from what "findaliases" would do.

parser: add short comment how aliases are expanded in phases

parser: reorder alias expansion routine to return early I think it improves readability to move trivial cases first, and unindent blocks.

parser: move functions that process alias expansion to rule-set class They will be commonly used by revset and templater. It isn't easy to understand how _expand() works, so I'll add comments by a follow-up patch. The local variable 'alias' is renamed to 'a' to avoid shadowing the global 'alias' class.