Snapshot PPA installs older snapshot over newer release

[blandin]

Describe the bug
When a user already has the latest release installed from the Ubuntu PPA, attempting to switch to development snapshots results in the user receiving an older snapshot.

Steps to Reproduce
Steps to reproduce the behavior:

1. Install Mumble from release PPA
2. Add snapshot PPA
3. apt update && apt install mumble

Expected behavior
The installed mumble package should be no older than the latest version from the release PPA.

Desktop (please complete the following information):

• OS: Ubuntu
• Version: Mumble 1.3.1 (release), Mumble 1.3.1 RC1 (snapshot, OLDER than release)

[Krzmbrzl]

I think this is a problem of PPAs and not Mumble, isn't it? I guess as soon as you switch the PPA, it doesn't know about the newer version anymore and thus wants to "update" to the newer one.

Did you verify that this is not the case with other PPAs?

[blandin]

I mean, a PPA is just a repo with syntax glitter, and dpkg is going to resolve upgradability the same way it always does. I'm pretty sure this problem is due to how the packages are versioned. dpkg sees "1.3.1-1..." installed and thinks the available version "1.3.1-rc1..." is newer because "r" has a higher value than "1".

Either a semantic versioning scheme or appending "-dev" to the snapshot version number and "-stable" or "-release" to the release version number (because "s" and "r" have higher values than "d"; e.g. "1.3.1-stable") would fix this.

[blandin]

Also, to clarify: I did not remove the release PPA from /etc/apt/sources.list.d/. With both PPA repos configured, apt still wants to "upgrade" from the release version to the older snapshot.