bug#17628: Strange output from C-x v =

[Glenn Morris]

Richard Stallman wrote:

> changes shown below.  The strangeness is, why does it output
> "No changes between working revision and workfile." before
> showing the differences between them?

It doesn't do that for me.
Looking at vc-diff-internal shows that message comes from:

    (if (and (zerop (buffer-size))
             (not (get-buffer-process (current-buffer))))
        ;; Treat this case specially so as not to pop the buffer.
        (progn
          (message "%s" (cdr messages))
          nil)

so I'm going to guess that this is just a manifestation of the same
process-handling-related issue you have been seeing with epg.
Emacs mistakenly thinks the process has exited before it has had a
chance to return anything.