If applied, this commit will introduce a new `--insecure-repository`
flag to the following commands: `push artifacts`, `pull artifact`,
`diff artifact` and `list artifacts`. When used the flag will lead to
the option `crane.Insecure` being passed to the `crane` client allowing
the use of insecure repositories.
Signed-off-by: Matthieu Mottet <m.mottet@outlook.com>
