rebase: reduce scope of a variable
Differential Revision: https://phab.mercurial-scm.org/D3940
context: rename descendant() to isancestorof()
This makes the direction much clearer, IMO.
Differential Revision: https://phab.mercurial-scm.org/D3936
copies: delete now-unnecessary check for "a == b" before "a.descendant(b)"
Unnecessary since
879cbdde63df (revlog: do inclusive descendant
testing (API), 2018-06-21).
Differential Revision: https://phab.mercurial-scm.org/D3935