Throw an error if a specified tag does not exist. Also make sure that
the user input is normalized as we already do for `podman tag`.
To prevent regressions, add a set of end-to-end and systemd tests.
Last but not least, update the docs and add bash completions.
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>
Add an exists subcommand to podman container and podman image that allows
users to verify the existence of a container or image by ID or name. The return
code can be 0 (success), 1 (failed to find), or 125 (failed to work with runtime).
Issue #1845
Signed-off-by: baude <bbaude@redhat.com>