This is a rather-messy, complex change to get the "command" package
building again against the new backend API that was updated for
the new configuration loader.
A lot of this is mechanical rewriting to the new API, but
meta_config.go and meta_backend.go in particular saw some major
changes to interface with the new loader APIs and to deal with
the change in order of steps in the backend API.
The state locking improvements for the regular command had the side
effect of locking the state in the console, import, graph and push
commands. Those commands had been updated to get a state via the
Backend.Context method, which locks the state whenever possible, and now
need to call Unlock directly.
Add Unlock calls to all commands that call Context directly.
Previously we required callers to separately call .Validate on the root
module to determine if there were any value errors, but we did that
inconsistently and would thus see crashes in some cases where later code
would try to use invalid configuration as if it were valid.
Now we run .Validate automatically after config loading, returning the
resulting diagnostics. Since we return a diagnostics here, it's possible
to return both warnings and errors.
We return the loaded module even if it's invalid, so callers are free to
ignore returned errors and try to work with the config anyway, though they
will need to be defensive against invalid configuration themselves in
that case.
As a result of this, all of the commands that load configuration now need
to use diagnostic printing to signal errors. For the moment this just
allows us to return potentially-multiple config errors/warnings in full
fidelity, but also sets us up for later when more subsystems are able
to produce rich diagnostics so we can show them all together.
Finally, this commit also removes some stale, commented-out code for the
"legacy" (pre-0.8) graph implementation, which has not been available
for some time.
There was no cancellation context for a plan, so it would always have to
run to completion as SIGINT was being swallowed.
Move the shutdown channel to the command Meta since it's used in
multiple commands.
Instead of providing the a path in BackendOpts, provide a loaded
*config.Config instead. This reduces the number of places where
configuration is loaded.
Martin Atkins