Previously our man pages included the current time each time they were
generated. This causes an issue for reproducible builds, since each
re-build of a package that includes the man pages will have different
times listed in the man pages.
To fix this, add support for SOURCE_DATE_EPOCH (which is a standardised
packaging environment variable, designed to be used specifically for
this purpose[1]). spf13/cobra doesn't support this natively yet (though
I will push a patch for that as well), but it's simpler to fix it
directly in docker/cli.
[1]: https://reproducible-builds.org/specs/source-date-epoch/
Signed-off-by: Aleksa Sarai <asarai@suse.de>
Also consolidate the leftover packages under cli.
Remove pkg/mflag.
Make manpage generation work with new cobra layout.
Remove remaining mflag and fix tests after rebase with master.
Signed-off-by: Daniel Nephin <dnephin@docker.com>