Broken link to edit docs, perhaps should link to repo instead of directory to avoid having a branch in the URL. Also added blurb to clarify what branch doc edits should occur in.
The current guides have a few areas where they recommend an approach that is more complex than what most people take.
- Rebase straight onto upsteam/msaster
- Force push a rebased branch
I also fixed the conflict resolution help to be relevant to rebase commands, and kept the push instruction out of the rebase instruction.
I don't know what that release candidate branch stuff is, but:
* I've never seen any of the core team do it
* I think it's overkill for most patches
* I think it's being too prescriptive: if contributors want to do that, that's cool, but it doesn't affect the core team.
* It makes our contributing guidelines more complex than they need to be.
The guidelines for contributing code were scattered across a section of contributing.md and collaboration-on-git.md. I've updated this to have separate contributing/code.md page with all the content in a single cohesive page. We also have contributing/documentation.md, contributing/issues.md and contributing/translation.md.
