copies-rust: hide most of the comparison details inside a closure...
copies-rust: hide most of the comparison details inside a closure
The function that compares values needs various supporting elements that are
the same for each call. We are about to both make change to these element and
change to call sites in our upcoming work. So abstracting most of the details
will help to avoid conflict while these works happen in parallel.
Differential Revision:
https://phab.mercurial-scm.org/D9426
