[Proposal] Simplify upstream version string rule

[Benjamin Mesing <bensmail@gmx.net>]

[please CC, I am not subscribed]

Hello,

currently the policy has the following rule for upstream version
strings:
        The upstream_version may contain only alphanumerics[33] and the
        characters . + - : (full stop, plus, hyphen, colon) and should
        start with a digit. If there is no debian_revision then hyphens
        are not allowed; if there is no epoch then colons are not
        allowed.

I would suggest to change it to:
        The upstream_version may contain only alphanumerics[33] and the
        characters . + (full stop, plus) and should start with a digit.

To allow hyphen and colon complicates the definition and I believe has
small benefit. If upstream version contains such characters, those could
be easily replaced (as it is currently done with different characters.
The following commandline can be used to identify the number of packages
that actually use hyphens in the upstream version number:
        # apt-cache dumpavail | perl -e 'foreach(<>) { if (/^Version:/) { if (/.+-.+-.+/) {print} } }'|wc -l 
        518
which is roughly 2.5% of the archive and for the colon:
        # apt-cache dumpavail | perl -e 'foreach(<>) { if (/^Version:/) { if (/\d+:.+:.+/) {print} } }'|wc -l
        0
which is 0% of the archive.

I think the simplification would be worth the effort to fix those 518
packages (where many share a common source package). If you disagree, at
least the colon could be totally forbidden.

Best regards

Ben