X.A.DynamicWorkspaces: Remove duplicates when melding

[slotThe]

Lest we forget to include this in the new release, I took the liberty of packing @liskin's fix up as a PR. We should probably still the root cause of it all, but I see us not having the time for that in the new few days (mid-October, folks!). Hence this only refers to the issue as Related: and not Fixes: (even though it does fix the problem, but I figured an open issue would give us some more motivation down the road than a closed one),

Description

When removing a workspace and distributing its windows, it's important to remove any duplicates that may be there due to, for example, usage of X.A.CopyWindow. X will only draw one of these window, leading to some artifacts.

Related: https://github.com/xmonad/xmonad-contrib/issues/565

Co-authored-by: Tomas Janousek tomi@nomi.cz

Checklist

• [x] I've read CONTRIBUTING.md

• [x] I've considered how to best test these changes (property, unit, manually, ...) and concluded: @ixzh confirmed that this fixes their issue in https://github.com/xmonad/xmonad-contrib/issues/565

• [x] I updated the CHANGES.md file

• [n/a] I updated the XMonad.Doc.Extending file (if appropriate)

[slotThe]

As far as users of DynamicWorkspaces are concerned, this does fix the bug, so a changelog entry might actually be in order?

Mh I think you're right; I've added something

[liskin]

Thanks! I removed #565 from the 0.17 release project for now.