Fix installation of metapackages on cmdline

[DasSkelett]

Problem

When trying to install metapackages from cmdline, using ckan.exe -c metapackage.ckan, it doesn't actually install any mods:

$ mono ckan.exe install --instance "Fake-1.11.2" -c asdf.ckan 
About to install:


Continue? [Y/n] 
Updating registry
Committing filesystem changes
Rescanning GameData
Done!

whereas the GUI installs them correctly.

Cause

In InstallList(List<string> modules, ...), we are running the RelationshipResolver for the identifier list, to get back a list of CkanModule to install. Then we filter out all modules installed as dependencies, to make sure the resolver running in InstallList(ICollection<CkanModule> modules, ...) can re-detect them as dependencies, so we can mark them as auto-installed.

CKAN/Core/ModuleInstaller.cs

Lines 108 to 113 in 72c4a56

	public void InstallList(List<string> modules, RelationshipResolverOptions options, RegistryManager registry_manager, ref HashSet<string> possibleConfigOnlyDirs, IDownloader downloader = null)
	{
	var resolver = new RelationshipResolver(modules, null, options, registry_manager.registry, ksp.VersionCriteria());
	// Only pass the CkanModules of the parameters, so we can tell which are auto
	InstallList(resolver.ModList().Where(m => resolver.ReasonFor(m) is SelectionReason.UserRequested).ToList(), options, registry_manager, ref possibleConfigOnlyDirs, downloader);
	}

The problem with metapackages is, that the first RR filters them out of the mod list (we don't want to actually install the metapackage after all). Thus the list of mods passed to InstallList(ICollection<CkanModule> modules, ...) is empty.

Changes

Now we also keep modules whose selection reason is "I'm a dependency|recommendation|suggestion of a metapackage" in the list passed to InstallList(ICollection<CkanModule> modules, ...) .
The InstallList(List<string> modules, ...) method is only used in the CmdLine; GUI sends the metapackage as CkanModule to InstallList(ICollection<CkanModule> modules, ...), and the ConsoleUI pretty much only deals in CkanModules (and doesn't have a "Install from .ckan" feature).

InstallList() is now also returning early if there are no mods to install, no need to go through the whole transaction and registry saving shebang.

I was considering two other solutions:
b) make CmdLine.Install.RunCommand()) call the other InstallList() passing a list of CkanModule instead of identifier+version combos. This might or might not have introduced other issues causing installation of outdated modules (I think we moved to a list of strings some time ago deliberately?)
c) make RelationshipResolver.Resolve() mark dependencies of metapackages as SelectionReason.UserRequested, not Depends. Might have had other side effects as well.

[HebaruSan]

Will this work for a metapackage that uses recommends instead of depends?

What about a metapackage with suggests, when the user passes --with-suggests and/or --with-all-suggests?

Maybe we should check reason.Parent?.IsMetapackage regardless of the reason type.

[DasSkelett]

Good point, changed it to keep all relationships of metapackages.

[HebaruSan]

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