pypa/pip — pull request #1492 by qwcode (2014-01-22 02:13:53+00:00)
Title: also try the legacy matcher when determining prereleases

2 changes here:

1. our prerelease function now additionally tries the legacy matcher, when normalization fails (i.e. when it fails to be close to PEP426). this specifically makes it so something like "1.3-fork1" will *not* be called a prerelease
2. we now use the distlib `is_prelease` properties, which were added after our function was added.