git skip update does not work for some repos

[schmunk42]

ie. for several repos with a dash, but also async

Adding VCS repository npm-asset/csv-parse
(skip update) Adding VCS repository npm-asset/lodash
(skip update) Adding VCS repository npm-asset/esprima
(skip update) Adding VCS repository npm-asset/test262
Adding VCS repository npm-asset/async
(skip update) Adding VCS repository npm-asset/minimist
Adding VCS repository npm-asset/wordwrap
(skip update) Adding VCS repository bower-asset/jquery-growl
Adding VCS repository npm-asset/optimist

I think it's related to:

composer-asset-plugin/Repository/Vcs/GitDriver.php

Line 90 in dd559b0

$this->repoDir = $this->config->get('cache-vcs-dir').'/'.preg_replace('{[^a-z0-9.]}i', '-', $this->url).'/';

But I wasn't able to figure out the exact root cause.