Martin von Zweigbergk <martinvonz@google.com> [Wed, 06 May 2020 11:40:17 -0700] rev 44884
copy: give better error message when no source paths found with --at-rev
The new error message matches what we show when marking copies in the
working copy.
Differential Revision: https://phab.mercurial-scm.org/D8496