templatekw: make getrenamed() return only filename, not nodeid
No callers cared about the nodeid and I want to make getrenamed() not
look up the node (although it's currently free, I hope to store copy
info in changesets and not include the nodeid).
Differential Revision: https://phab.mercurial-scm.org/D3666
% creating repo
% add and commit
C test.py
% change
M test.py