commit 71ebbb81ae replaced the use of the
custom "cli.Errors" type for stdlib's errors.Join, however it made a
mistake by calling errors.Join for each error occurred, which "nests"
each error instead of putting each error at the same level.
Thanks to Paweł Gronowski for spotting this on the [pull request][1]
[1]: 71ebbb81ae (r1810257735)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>