Review references to Subversion given github move

[Marc Tamlyn]

There are a few process-docs (release cycle, contibuting etc) which are still making the assumption that the root repo for django is the svn source. Would be good to go through this and tidy them up.

[Aymeric Augustin]

Yes. This item is on the TODO list but I don't think we ever created a ticket. Here's what must be done:

• Define the new guidelines for the community and for the committers. Discussion here: ​https://groups.google.com/group/django-developers/browse_thread/thread/b238bbe8b0cd7453
• Move internals/svn.txt to internals/git.txt and rewrite it. Also do a sweep search / replace to remove all references to Subversion.
• Include the grafts file built by Ramiro and instructions on how to use it: ​https://github.com/ramiro/django-git-grafts

[Aymeric Augustin <aymeric.augustin@…>]

In [90fb6a46485d4f3c70d3864ab0a0e2f619449d31]:

Fixed #18436 -- Updated contributing docs for git.

Most of the credit for this large patch goes to Anssi Kääriäinen.
Many thanks to all the people who contributed to the discussion.

[Preston Holmes]

​https://github.com/django/django/commit/90fb6a46485d4f3c70d3864ab0a0e2f619449d31

I jumped to the conclusion that the git commit referenced the wrong ticket number in the commit message, actually I can see they are related - I guess the proper thing in hindsight would have been that this should have been marked a dupe of #18307

Sorry for adding to the confusion.

[Aymeric Augustin]

I killed two birds with one stone :)