src/vs/platform/workspaces/common/workspaces.ts/massagePathForWindows
function massagePathForWindows(folderPath: string) {

	// Drive letter should be upper case
	folderPath = normalizeDriveLetter(folderPath);

	// Always prefer slash over backslash unless
	// we deal with UNC paths where backslash is
	// mandatory.
	if (!isUNC(folderPath)) {
		folderPath = toSlashes(folderPath);
	}

	return folderPath;
}