extensions/git/src/commands.ts/CommandCenter/stageAllMerge
class CommandCenter:	async stageAllMerge(repository: Repository): Promise<void> {
		const resources = repository.mergeGroup.resourceStates.filter(s => s instanceof Resource) as Resource[];
		const { merge, unresolved, deletionConflicts } = await categorizeResourceByResolution(resources);

		try {
			for (const deletionConflict of deletionConflicts) {
				await this._stageDeletionConflict(repository, deletionConflict.resourceUri);
			}
		} catch (err) {
			if (/Cancelled/.test(err.message)) {
				return;
			}

			throw err;
		}

		if (unresolved.length > 0) {
			const message = unresolved.length > 1
				? l10n.t('Are you sure you want to stage {0} files with merge conflicts?', merge.length)
				: l10n.t('Are you sure you want to stage {0} with merge conflicts?', path.basename(merge[0].resourceUri.fsPath));

			const yes = l10n.t('Yes');
			const pick = await window.showWarningMessage(message, { modal: true }, yes);

			if (pick !== yes) {
				return;
			}
		}

		const uris = resources.map(r => r.resourceUri);

		if (uris.length > 0) {
			await repository.add(uris);
		}
	}