gistfile1.txt

@dstufft makes the point that fred==1.0.1 could represent fred…tar.gz,
fred…zip, or fred…wheel, etc. Right now, we don't care about the extension; we
just extract the package name from the downloaded file by means of a cheesy
heuristic. But what if an index entry makes available both a zip and a tarball?
Which does pip favor? With the current syntax, we support only a single hash. I
suppose we could count on pip keeping its format-favoring behavior stable over
time. Are we going to have a problem here?