[Distutils] .egg-info metadata

[Daniel Holth]

> And they answer most of your questions.  A few call-outs below:
>
>> dependency_links.txt: url's of the package's dependencies. Speak up if
>> you use this; it is very surprising, and has a much better replacement
>> with pip --index options and requirements files.

I will check to see how often this is used.

> No, actually, those are not replacements at all, let alone better
> ones.  They're for a package's supplier to offer third-party builds to
> fulfill requirements not available via PyPI.  E.g. the author of
> package Foo offers unofficial Windows builds of package Bar, and
> includes dependency links so that those dependencies can be fulfilled
> even if not present on PyPI.

It's probably a style thing, but I like to distribute this information
out-of-band. So as the author of foopackage (an application) I list
all the requirements and their requirements and where they can be
found, including git+http://github urls and so forth. I'm sure this
has all been discussed to death over the last 6+ years.

>> Provides works the same way in setuptools, it is in PKG-INFO.
>
> Setuptools doesn't actually use Provides.

I noticed that. An installer could generate a file
provided-name.egg-info based on this information. Ironically
distribute would probably be the main client of this feature.

> Lexical formats of the files are described in terms of pkg_resources
> API calls -- these calls (and more precise syntax documentation) are
> documented here:
>
>   http://peak.telecommunity.com/DevCenter/PkgResources
>
> Mainly in the "Parsing Utilities" section:
>
>   http://peak.telecommunity.com/DevCenter/PkgResources#parsing-utilities

I am impressed by pkg_resources.