branch heads: fix regression introduced in
e67e5b60e55f (
issue1726)
For merge nodes it is not adequate to only check a single possible
branch head for whether it is an ancestor of the latest head, but it
needs to be done for each possible branch head.
% convert while testing all possible outputs
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% check tags are in UTF-8
'1c1b4062874e8197a68e7ce9e498479a37d0215c branch\xc3\xa9e\n'
'edc96568720ef79eefa6372677b18d855de3abee branch\xc3\xa9\n'