Refactor: Change Registry Function Pointer Types to Option<fn()>

[allaboutevemirolive]

For context: https://doc.rust-lang.org/beta/std/primitive.fn.html

trees-rs/src/config/registry.rs

Lines 30 to 56 in a5a9058

	pub struct Registry<'a> {
	// Common util
	read: FnReadDir,
	sort: FnSortEntries,
	// Entry
	pub dir: FnOutDir<StdoutLock<'a>>,
	pub file: FnOutFile<StdoutLock<'a>>,
	pub symlink: FnOutSymlink<StdoutLock<'a>>,
	pub head: FnOutHead<StdoutLock<'a>>,
	// Metadata
	pub pms: FnExtPermission<StdoutLock<'a>>,
	pub btime: FnExtBTime<StdoutLock<'a>>,
	pub mtime: FnExtModTime<StdoutLock<'a>>,
	pub atime: FnExtAccessTime<StdoutLock<'a>>,
	pub size: FnExtSize<StdoutLock<'a>>,
	// Color
	reset: FnColor<StdoutLock<'a>>,
	yellow: FnColor<StdoutLock<'a>>,
	bold_red: FnColor<StdoutLock<'a>>,
	underlined_blue: FnColor<StdoutLock<'a>>,
	blue: FnColor<StdoutLock<'a>>,
	green: FnColor<StdoutLock<'a>>,
	purple: FnColor<StdoutLock<'a>>,
	}

[allaboutevemirolive]

I'm not convinced about this implementation. All fields will be called regardless of whether they're used, so wrapping the type in Option seems unnecessary.

The key difference is that using Option requires us to check or unwrap it for every folder iteration. Without Option, we can avoid these extra steps, either calling a function that performs an action or a no-op function.