Briefcase v0.3.12.dev0+xxx is not Treated as a Dev Version

[rmartin16]

Describe the bug
The dev attribute of a packaging.version.Version object is the number from dev# in the version. When the number is 0, the version is not treated as a dev version.

create.py

            # If we're on a development branch, and the template branch was *not*
            # provided explicity, we can use a fallback development template.
            # Otherwise, re-raise the exception about the unsupported template version.
            if version.dev and app.template_branch is None:

new.py

            # If we're *not* on a development branch, raise an error about
            # the missing template branch.
            if not version.dev:
                raise

❯ python
Python 3.10.7 (main, Sep 28 2022, 17:55:46) [GCC 11.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from packaging.version import Version
>>> Version('0.3.12.dev1+gf0e822f.d20221016').dev
1
>>> Version('0.3.12.dev0+gf0e822f.d20221016').dev
0

To Reproduce
Steps to reproduce the behavior:
Run briefcase create or briefcase new with a dev0 version.

Expected behavior
dev0 versions are dev versions.

Environment:

• Operating System: Ubuntu 22
• Python version: 3.10
• Software versions:
  • Briefcase: 0.3.12.dev0+gf0e822f.d20221016

[freakboy3742]

Ah - I saw this, and 🤦 . The irony is that by applying this patch, the problem goes away... because you're no longer on dev0+ :-)