Add a commented-out CopySuite.TestRunShell
Add a commented-out CopySuite.TestRunShell

We are maintaining code to set up and run registries, including the
fairly complex setup for Atomic Registry, in the integration tests.
This is all useful for experimentation in shell, and the easiest way to
do that is to add a “test” which, after all the set up is done, simply
starts a shell.

This is gated by a build tag, so it does not affect normal test runs.

A possible alternative would be to convert all of the setup code not to
depend on check.C and testing.T, but that would be fairly cumbersome due
to how prevalent c.Logf and c.Assert are throughout the setup code.
Especially the natural replacement of c.Assert with a panic() would be
pretty ugly, and adding real error handling to all of that would make
the code noticeably longer.  The build tag and copy&pasting a command
works just as well, at least for now.

(It is not conveniently possible to create a new “main program” which
manually creates a check.C and testing.T just for the purpose of running
the setup code either; check.C can be created given a testing.T, but
testing.T is only created by testing.MainStart, which does not allow us
to submit a non-test method; and testing.MainStart is excluded from the
Go compatibility promise.)

jwhonce/skopeo,mtrmac/skopeo,projectatomic/skopeo,jwhonce/skopeo,mtrmac/skopeo,projectatomic/skopeo,mtrmac/skopeo