Git decorations not shown in Explorer on startup

[colin-grant-work]

Bug Description:

Steps to Reproduce:

1. In a source controlled folder...
2. Add a file.
3. Start the application with that folder as your workspace (and no editors open - recommended but usually not required)
4. Observe that the new file is not marked as untracked in the explorer.
5. Trigger a Git event (e.g. check out a different commit)
6. Observe that the file is now marked as untracked.

Additional Information

A few lifecycle issues contribute to this problem:

The Git decorations are contributed to the core DecorationsService here:

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

Lines 284 to 289 in 62ddc03

	onStart(): void {
	this.updateStatusBar();
	this.repositoryTracker.onGitEvent(() => this.updateStatusBar());
	this.syncService.onDidChange(() => this.updateStatusBar());
	this.decorationsService.registerDecorationsProvider(this.gitDecorationProvider);
	}

But that onStart method may be (and usually is) called after Git has started up and the gitDecorationProvider has fired its first few events.

Then the decorations from the DecorationsService reach the Explorer via the FileTreeDecoratorAdapter here:

theia/packages/filesystem/src/browser/file-tree/file-tree-decorator-adapter.ts

Lines 43 to 46 in 62ddc03

	this.decorationsService.onDidChangeDecorations(newDecorations => {
	this.updateDecorations(this.decorationsByUri.keys(), newDecorations.keys());
	this.fireDidChangeDecorations();
	});

But again, if the DecorationsService has already fired events by the time the FileTreeDecoratorAdapter is constructed, the latter won't catch those events, and the DecorationsService provides no API to discover all known decorations at a given time.

• Operating System: RHEL7
• Theia Version: 1.34.1