f14eeeb361
hostVar is used for the '--host' / '-H' flag to set [ClientOptions.Hosts].
The [ClientOptions.Hosts] field is a slice because it was originally shared
with the daemon config. However, the CLI only allows for a single host to
be specified.
hostVar presents itself as a "string", but stores the value in a string
slice. It produces an error when trying to set multiple values, matching
the check in [getServerHost].
[getServerHost]: 7eab668982/cli/command/cli.go (L542-L551)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>