bug#19296: [PATCH] Package archives now have priorities.

[Stefan Monnier <monnier@iro.umontreal.ca>]

> When installing packages by name, only packages from archives with
> the highest priority are considered, before versions are compared.

What can this be used for (other than the MELPA case, obviously)?

> This solves the "MELPA problem", where MELPA assigns date-based
> version numbers to packages which override all other archives.
> Giving MELPA a lower priority means packages are installed from
> MELPA only when the package is not available from other archives.

I think the better way to solve the problem of versioning the "bleeding
edge package" would be to take the base version and tuck the date to it
(instead of only using the date).
I.e. file names like foo-mode-1.3.0.20141023.tar.gz where "1.3" is the
version of the last release.

Of course that requires a change on MELPA side and I have no idea how
easy/feasible that would be.  And I'm not completely sure it would
really be the best option either.

But maybe an idea along the same lines would be to treat revision
numbers of the form YYYYMMDD (or similar) as being a "bleeding edge"
release and to translate them to, "0.0.YYYYMMDD".
This would have a similar effect to setting MELPA's priority lower.

> This can be overridden manually by the user.

An important issue is what happens after the user did such an override.
In my above suggestion, the behavior would kind of suck since
package-list would then constantly recommend "upgrading" to the
official release (since 1.3 is "more uptodate" than "0.0.YYYYMMDD").


        Stefan