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.
% new file
applying patch from stdin
% new empty file
applying patch from stdin
empty
% chmod +x
applying patch from stdin
% copy
applying patch from stdin
a
a
% rename
applying patch from stdin
copyx
empty
new
rename
% delete
applying patch from stdin
empty
new
rename
% regular diff
applying patch from stdin
% copy and modify
applying patch from stdin
a
a
b
a
a
% rename and modify
applying patch from stdin
a
a
b
c
a
% one file renamed multiple times
applying patch from stdin
9 rename2 rename3 rename3-2 / rename3 (rename2)rename3-2 (rename2)
rename3
rename3-2
a
a
b
c
a
a
a
b
c
a
% binary files and regular patch hunks
applying patch from stdin
foo
045c85ba38952325e126c70962cc0f9d9077bc67 644 binary
% many binary files
applying patch from stdin
045c85ba38952325e126c70962cc0f9d9077bc67 644 mbinary1
a874b471193996e7cb034bb301cac7bdaf3e3f46 644 mbinary2
% filenames with spaces
applying patch from stdin
foo
% copy then modify the original file
applying patch from stdin
foo