Martin von Zweigbergk <martinvonz@google.com> [Thu, 09 May 2019 15:09:07 -0700] rev 42373
copies: split up _chain() in naive chaining and filtering steps
The function now has two clearly defined steps. The first step is the
actual chaining. This step is very cheap. The second step is filtering
out invalid copies. This step is expensive. For changeset-centric copy
tracing, I want to do the filtering step only at the end. This patch
prepares for that.
Differential Revision: https://phab.mercurial-scm.org/D6418