[opus] Unknown versions in git.

[Timothy B. Terriberry]

bat guano wrote:
> How about giving them versions like this:-
> 1.1-git and 0.1.7-git
> Or even incorporate the commit.

We do this. See the update_version script. "unknown" usually means this 
script failed to extract a version for some reason (couldn't run git, or 
your git version was too old). For example, with git 1.5.6.1, the git 
describe command fails with "error: unknown option `dirty'", which 
results in version "unknown", but with a recent version of git it works.