From: Paolo Bonzini <bonzini@gnu.org>
Date: Fri, 28 Aug 2009 15:50:28 GMT
Subject: Re: Using git to track my PhD thesis, couple of questions
Message-ID: <4A97FCC4.5070808@gnu.org>
In-Reply-To: <20090828133708.GA11146@kisimul>

On 08/28/2009 03:37 PM, seanh wrote:
> In response to Matthieu and Paolo, I'm not sure I understand the git
> internals involved in the discussion around merge --squash, I had a
> feeling this would produce a 'merge' that git in some sense would 'not
> know about', since it sounds complex and I don't understand it I don't
> think I want to go there.

Yes, the problem is that git does not track what happens when you do 
"git merge --squash", which makes it harder to do merges after some time 
(because of conflicts).

The solution I gave (and Matthieu explained how it works, even though 
it's very technical) is a way to "explain" git what you did.  If you try 
it on a fake example with gitk, you should understand it better.

    mkdir test
    cd test

    # import
    git init
    echo a > test
    git add a
    git commit -m1

    # some changes happen in your local "fine grained" branch
    git checkout -b local
    echo b > test
    git commit -a -m2
    echo c >> test
    git commit -a -m3                                  ##<<<

    # the magic incantation brings those commit to master
    # (first two commands) and teaches git what happened (last two)
    git checkout master
    git merge --squash local; git commit -m'merge 1'   ##<<<
    git checkout local
    git merge master                                   ##<<<

    # more local changes
    sed -i s/b/d/ test
    git commit -a -m4
    echo z >> test
    git commit -a -m5                                  ##<<<

    # the magic incantation, again
    git checkout master
    git merge --squash local; git commit -m'merge 1'   ##<<<
    git checkout local
    git merge master                                   ##<<<

Use gitk at the points indicated with ##<<<

It is actually very similar to what you chose to do.  My commits to 
master, in practice, are your tags.  You may want to see how gitk's 
graphs looks in both scenarios, and choose the one that you prefer.

Hope this helps!

Paolo