In the current PKGREVISION thread, from time to time there appears the 
statement:

     PKGREVISION should be changed whenever the binary package changes.

In which cases do we consider a binary package to be changed?

Just comparing the checksums of binary.tgz does not work because the 
timestamps of the +META files are different for each build.

I see two other possibilities:

1. A file from the PLIST has changed.

2. The behavior of the package has changed.

Maybe there are more.

Roland