Squash to only one "proper" commit for github pull request

Question

I have a repo on github which someone else (Bob, for the sake of argument) has issued a pull request for. His code's not perfect, so we go through a few rounds of markups. As I understand it, he commits and pushes to his pull-request for each set of marked up changes.

So my repository now looks like this:

master: ---o A (Chowlett
           |
           |
pull-req:  o---o---o---o
               B   C   D (all Bob)

Commit SHAs and msgs are as follows:

A:

123456 Good commit <chowlett>

B:

777ccc Fix the widget bug <bob>

C:

888ddd Review markups <bob>

D:

999eee Further markups <bob>

I'm now happy to accept this pull request; but I'd rather the pre-markup versions weren't in my repo. Can I achieve all of the following; and how?

• Merge B, C & D into my repo as a single commit
• Generate the "Merge pull request #99 into ..." commit as well
• Have github automatically close the pull request

Answer 1

Note that Bob doesn't have to squash his commits when he is making a GitHub PR.
Since March 2016, you can leave that operation to the maintainer (you) accepting your PR.

See "Squash your commits" and its new documentation

This is a new option which lets you force commit squashing on all pull requests merged via the merge button.