Presently, when preparing an update version, we must target the previous version. Typically this is the last released version, so a fixed version comparison (as a string) is sufficient. But in the case of the 4.5 update where we had to prepare two additional helper patches which were in development simultaneously (and on SNAPSHOT).
The improvement requested is that an origin version could be treated as a regex or base version that allows SNAPSHOTs on same version to "qualify" for matching. That is, if update.json specifies
that either 4.0.0-2 (released), 4.0.0-2-SNAPSHOT, or 4.0.0-2-RC2 would be considered an appropriate origin.
An alternate approach would be to support version ranges, but this is perhaps more iffy.