This change repivots the plan/apply commands slightly. This is largely
in preparation for performing deletes and updates of existing environments.
The old way was slightly confusing and made things appear more "magical"
than they actually are. Namely, different things are needed for different
kinds of deployment operations, and trying to present them each underneath
a single pair of CLI commands just leads to weird modality and options.
The new way is to offer three commands: create, update, and delete. Each
does what it says on the tin: create provisions a new environment, update
makes resource updates to an existing one, and delete tears down an existing
one entirely. The arguments are what make this interesting: create demands
a MuPackage to evaluate (producing the new desired state snapshot), update
takes *both* an existing snapshot file plus a MuPackage to evaluate (producing
the new desired state snapshot to diff against the existing one), and delete
merely takes an existing snapshot file and no MuPackage, since all it must
do is tear down an existing known environment.
Replacing the plan functionality is the --dry-run (-n) flag that may be
passed to any of the above commands. This will print out the plan without
actually performing any opterations.
All commands produce serializable resource files in the MuGL file format,
and attempt to do smart things with respect to backups, etc., to support the
intended "Git-oriented" workflow of the pure CLI dev experience.
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