[Xmonad] darcs patch: add CopyWindow module, to support sticky/tagged windows.

[Donald Bruce Stewart]

droundy:
> Hi all,
> 
> Here's support for sticky windows and dwm-style tagging.  Requires (I
> believe) my improved delete.  It almost duplicates code in StackSet, since
> I wanted to make as few modifications as possible.  So by default, insertUp
> will refuse to act on sticky windows, and shift will delete a sticky window
> from all workspaces but one.
> 
> We can later decide if we want to change their behavior in core to behave
> well with sticky windows, or just duplicate it here.  My feeling is that
> this module eventually belongs in core, but that contrib is the right place
> to develop it.  kill1, for instance, I think could probably eventually
> replace kill (it behaves identically on non-sticky windows), and with
> changes to the quickcheck tests, insertUp' could replace insertUp.

I'm sympathetic to allowing sticky windows in extensions, but we're
close to feature cut off for 0.3. This kind of basic change is something
I'd like to look at immediately after 0.3 is released -- as we did with
the floating layer.

Unless there's a very compelling argument for it, I think we should just
sit on this patch till the day after 0.3 goes out. The alternative is a
single, clean patch, with accompanying QuickChecks stating precisely the
new semantics.

-- Don