Martin von Zweigbergk <martinvonz@google.com> [Fri, 22 Mar 2019 09:45:07 -0700] rev 4460
compat: add support for new arg name in memfilectx.__init__
This makes us compatible with 550a172a603b (memctx: rename constructor
argument "copied" to "copysource" (API), 2019-03-19).
evolve: compat patch to fix broken evolve obsdiscovery
This patch preserve the compatibility for the changes upstreamed
by e5ece0f46b40 in hg-committed.