Comment 4 for bug 1664235

Thank you. This is almost ready.

1. usr/share/appdata/ should be installed by peony not peony-common.

https://wiki.debian.org/AppStream/Guidelines#General

If you want upgrades to work correctly when moving files, you'll need to add Breaks/Replaces. Are people using that PPA? If so, I recommend bumping the version number to 1.0.0-0ubuntu2.
Then in debian/control, for peony, add
Breaks: peony-common (<< 1.0.0-0ubuntu2~)
Replaces: peony-common (<< 1.0.0-0ubuntu2~)

The trailing ~ is to make it easier for someone to backport in their PPA.

2. Very minor but you can use just 'Peony' in debian/copyright's Upstream-Name
If you want to mention caja, you can add a Comment: field

https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/#header-paragraph