Currently, airshipctl users switch their current context by modifying
the airshipctl config file or executing airshipctl config set-context
[NAME]. This change introduces the use-context subcommand, which
replaces the current behavior of using set-context without flags. After
this change, set-context will only be used to modify contexts.
Change-Id: If3980138a0abeeb6c59c07615b5373654073610a
Signed-off-by: Drew Walters <andrew.walters@att.com>
a437caa141