A copy --to a local git remote that gets interrupted and is run again does
not resume where it left off, but copies all the data again.

This does not affect git remotes accessed over ssh.

It's kind of hard to notice this, because normally a resume, has to read
the src file and dest file, in order for incremental verification to
get started. But it is somewhat slower to do that than it is to re-write
the dest file from the start. And when annex.verify = false, it's a lot
slower.

Looks like it's due to copyCoW unlinking the dest file. Since the first
file copy trues copyCoW to probe if that's supported, that happens.
And when resuming an interrupted copy, that probe will generally happen
with the file it was interrupted on.

So, the solution seems like it would be to copyCoW to some other temp file,
and if it succeeds, rename it to the dest.
--[[Joey]]

> [[fixed|done]] --[[Joey]]
