RFE: Optionally `dupemerge` before compacting

[TPS]

1. Hardlinking duplicate files before compacting,
2. & then tracking inodes during compacting would be beneficial.

dupemerge does № 1 well, & № 2 could be handled via code here.

Homepage: https://www.schinagl.priv.at/nt/dupemerge/dupemerge.html
Source repo:
https://gitlab.com/schinagl/link-shell-extension