git rebase backend change: post-checkout hook is not ran by 'merge' backend

[Philippe Blain <levraiphilippeblain@gmail.com>]

Hello,

I'm not sure if this has been reported yet (couldn't find it), 
but I noticed a behavioral difference between the merge 
and apply backends that is not mentioned in the documentation:
The 'apply' backend will run the post-checkout hook just after 
moving HEAD to the commit we are rebasing onto; 
this does not happen with the merge backend:

    $ echo "echo \"Running post-checkout hook\"" > .git/hooks/post-checkout
    $ git checkout -b <branch1> <commit2>
    $ git rebase upstream/master --apply
    First, rewinding head to replay your work on top of it...
    Running post-checkout hook
    Applying: <commit1>
    Applying: <commit2>
    $ git checkout -b <branch2> <commit2>
    Successfully rebased and updated refs/heads/<branch2>

Cheers,
Philippe.