[racket-dev] package source as a Git repo

The development version of the package manager now supports Git
repository references using "http[s]://" and sites other than GitHub.
That is, a package source can have the form

 git://host/[...]

for a host other than "github.com", and a source can have one of the
forms

 http://[...].git
 https://[...].git

which use the Git protocol over a "smart" HTTP(S) transport. In
particular, the "HTTPS" URL that appears on a GitHub repository page
will work directly as a package source.


Since generalized Git repository references are not supported in the
upcoming v6.1.1 release, it will be a while before you'll want to
publish package sources using the new forms.