There is an updated pull request by mtboehlke against master on the void-packages repository

https://github.com/mtboehlke/void-packages signify
https://github.com/void-linux/void-packages/pull/38590

signify: update to 31.
Edit: I also added changelog and removed the UPDATE file, which doesn't seem correct anymore.

Add needed libmd makedepend and tar checkdepend,
use vsed instead of sed for the file patching,
and use sed instead of head to extract a nicer LICENSE file

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A patch file from https://github.com/void-linux/void-packages/pull/38590.patch is attached