Meld in master has ‘support’ for being built as an xdg-app bundle. This hasn’t actually required any changes to Meld itself, just a script or two to do the necessary building + shims.
If you want to build your own bundle, you can clone current Meld from git, and then:
Yes, this will download another copy of Meld from git, even though you just
cloned it. Don’t think about it too much. This is just the result of me not
properly understanding the
xdg-app building model when I started, and the
building model being a little odd. I’m sure there is (or will be) a sane way
xdg-app building info and scripts in the repo you’re building, but
for now this appears to basically work.