When run fedpkg-new in a package repo where there is no tag, git-describe fails to get last tag and break new immediately. The output could confuse user and don't know what's wrong

$ fedpkg new
Could not execute new: 'git describe --tags --abbrev=0' returned with exit code 128
stderr: 'fatal: No names found, cannot describe anything.'

A suggestion would be to show a message like this

Cannot get latest changes because no tags in this repo.