Version numbers for snap packages

[Joseph Rushton Wakeling]

Hello all,

Quick question about version numbering (as in, the `version:` field of 
`snapcraft.yaml`).  The logical choice here is to use the version of the app 
being packaged, but what's the recommended way to handle changes to the snap 
package alone that don't change the version of the underlying app?

Is a scheme like x.y.z-n advisable (where n is the revision number of the snap 
itself for this version of the app), or are there alternative suggestions?

More generally, what are recommended practices for setting the `version:` field 
of snap packages?

Thanks & best wishes,

     -- Joe