Hi I've extended the bash-completion file proposed by Joseph Wang, which was extended from that by Alfredo Esteban.
I don't know about any licensing info that I should mention in the file, but I don't claim any rights on it, and anyone is free to modify/distribute with/without acknowledging me. I'd be happy if it could be distributed with btrfs-progs. I'm a relatively new btrfs user and am more than satisfied with it. Thank you for your great work developers. [Installation notes to general audience: probably copying this file to /usr/share/bash-completion/ completions/ should do it]
btrfs
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