or an example of how MacPorts does it, see port:543 (in proc get_outdated_ports). In pseudo-code, it says roughly:

†† if current_epoch != available_epoch †††† use epoch as basis for comparison †† else if current_version != available_version †††† use version as basis for comparison †† else †††† use revision as basis for comparison

This means that an epoch should never be removed, since if the epoch is different, it will always be used as the basis for comparison when listing outdated ports.

Some of the basis for confusion might come from macports.tcl:1923 (in proc upgrade), where the pseudo-code is roughly:

†† if current_version != available_version †††† use version as basis for comparison †† else †††† use revision as basis for comparison †† if current_epoch < available_epoch †††† upgrade anyway

Now that I've read it more thoroughly, this code actually *does* allow the epoch to be removed--eventually, once the updated version has been pushed out to everyone.

Hrm.

In other words, it seems that a port in which the epoch has been removed could still be upgraded (with e.g. `port upgrade active`), but would not be listed as outdated (and would not be upgraded with `port upgrade outdated`).

That's actually a bit of a mess and might deserve its own topic of discussion. For now, I think it should be stated that an epoch cannot be removed; this is the only case in which we can currently guarantee consistent behavior.

At the same time, we should change MacPorts' behavior to be consistent. I think the method from port(1) is better than the one from macports.tcl, since it's the only one in which we can guarantee upgrades correctly--even if it does force an extra line of cruft to hang around in Portfiles with epochs (all 20 of 'em!)

Chris, I changed the text to this based on what you said about current behavior. Let me know if it needs adjusting. ---------- An epoch is not needed for most ports. If an epoch is used it must never be decreased or removed even when a port's version is updated; this would cause port version comparisons to be incorrect since epochs take precedence over versions once epochs have been used. ---------- Mark