[SCM] Fix SCM status bar commands

[vinokurig]

What it does

Pass command arguments to SCM status bar commands. Pass Command.id to SCM status bar commands if Command.command is undefined.

How to test

1. Clone the test plugin: https://github.com/vinokurig/Test.git
2. Compile the plugin and start it as a hosted instance.
3. Select the / SCM repository (this is a view of a dummy SCM repository):
   
4. Click title button in the status bar:
   

See the notification

fixes eclipse-che/che#13974

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[akosyakov]

it not it confusing that id is used as command as well? Can we instead fix it in the plugin system, that id is assigned to a command. I don't think we should pull deprected apis in the plugin system into other extensions.

Also command and title are not optional in vscode.d.ts: https://github.com/microsoft/vscode/blob/6de911e3298424cfb6dd6792bff5499f1cd6a230/src/vs/vscode.d.ts#L19-L29

I wonder why there are optional for us? Can we fix it?

[vinokurig]

it not it confusing that id is used as command as well? Can we instead fix it in the plugin system, that id is assigned to a command.

done

Also command and title are not optional in vscode.d.ts: https://github.com/microsoft/vscode/blob/6de911e3298424cfb6dd6792bff5499f1cd6a230/src/vs/vscode.d.ts#L19-L29

I wonder why there are optional for us? Can we fix it?

The Git extension may set an SCM command item without an action:

theia/packages/git/src/browser/git-contribution.ts

Lines 647 to 652 in 2a97874

	if (this.syncService.isSyncing()) {
	return {
	title: '$(refresh~spin)',
	tooltip: 'Synchronizing Changes...'
	};
	}

[akosyakov]

after looking closer, actually it has to be id here, because this Command should be aligned with monaco command: https://github.com/microsoft/monaco-editor/blob/dc793af0020b9878b798b45fdcaf31e1b263c40b/monaco.d.ts#L5536-L5541, even though that vscode APIs are using command not id

I think we should fix typings here:

theia/packages/plugin-ext/src/common/plugin-api-rpc.ts

Lines 610 to 612 in eae45da

	acceptInputCommand?: ScmCommand;
	statusBarCommands?: ScmCommand[];
	}

i.e.:

acceptInputCommand?: Command;
statusBarCommands?: Command[];

since we actually send plugin commands not scm commands and then do adjustment in scm-main