1538
1538
:returns: One of: 'a_descends_from_b', 'b_descends_from_a', 'diverged'
1540
1540
heads = graph.heads([revision_a, revision_b])
1542
1542
return 'b_descends_from_a'
1544
1544
# These branches have diverged
1547
1547
return 'a_descends_from_b'
1549
1549
raise AssertionError("invalid heads: %r" % (heads,))