commands: Show less generic error when no manifest is loaded

[57300]

Minor quirk that stuck out to me while testing the recent changes. Before 23db6e1, if I were to try west manifest --resolve in Zephyr without cloning bsim, I would see this:

FATAL ERROR: project bsim (tools/bsim): cannot import contents of west.yml; do you need to run "west update"?

which is helpful enough. Now, this generic message gets displayed:

FATAL ERROR: can't run west manifest; it requires the manifest, which was not available. Try "west manifest --validate" to debug.

Ironically, west manifest --validate produces the same error, which is not very helpful. So, I tried to fix that.

[57300]

@mbolivar-nordic Hi, I can't add you as reviewer, but do you want to look over this?

[mbolivar-nordic]

I think this should probably be handled in the relevant built-in commands themselves by checking WestCommand.has_manifest and erroring out as necessary. Did you consider this? If so, why did you reject it?

[57300]

I think this should probably be handled in the relevant built-in commands themselves by checking WestCommand.has_manifest and erroring out as necessary. Did you consider this? If so, why did you reject it?

Yes, I had briefly considered it, but I figured it would probably involve passing WestApp.mle to each command, so that it could still report why not self.has_manifest. I decided against it, thinking it might be better to have common handling in one place. There's already some common handling in handle_builtin_manifest_load_err(), which seems to cover quite a few cases.

I'm fine with per-command handling, if you prefer, since it looks like only west manifest needs it right now anyway.

In fact, on second thought, the easiest fix for west manifest specifically might be to just remove it from this list:

west/src/west/app/main.py

Lines 277 to 283 in 9e8f500

	# A few commands are always safe to run without a manifest.
	# The update command is sometimes safe and sometimes not, but
	# we need to include it in this list because it's the only way
	# to fix a manifest-rev revision in a project which is being
	# imported to point from a bogus manifest to a non-bogus one.
	no_manifest_ok = ['help', 'config', 'topdir', 'init', 'manifest',
	'update']

since it will always bail without a manifest:

west/src/west/app/project.py

Lines 547 to 548 in 9e8f500

	def do_run(self, args, user_args):
	manifest = self.manifest