git branching plan

gistfile1.txt

--A-------B-------C--D------------E------F--- origin/trunk
       /      /           /           /
--------------------------------------------- upstream/trunk
    \                           \
     -- upstream/pkgsrc_2012Q2   -- upstream/pkgsrc_2012Q3

 - upstream/trunk is clean pkgsrc HEAD
 - origin/trunk tracks upstream/trunk periodically, and adds Joyent-specific    changes
 - pkgsrc gets branched every quarter

We want to:

 - Create quarterly release branches
 - Apply changes A-E, preserving history
 - Make it easy to cherry-pick F..

Suppose you want a new branch called "newbranch" which is based on upstream/pkgsrc_2012q3, but also has changes A to E.

I'd probably stare by creating the new branch from commit E,
then rebase the new branch onto upstream/pkgsrc_2012Q3.

Commit E is 2 commits before the head of origin/trunk,
so if you don't have a tag there, you can add one:

$ git tag base-for-newbranch origin/trunk~2

Use gitk to check that the tag is in the right place.

Then checkout that tag and create the branch:

$ git checkout base-for-newbranch
$ git branch newbranch

Now the tree looks like this:

                                      --------- newbranch
                     /
  --A-------B-------C--D------------E------F--- origin/trunk
 /     /         /          /          /
--------------------------------------------- upstream/trunk
    \                          \
     -- upstream/pkgsrc_2012Q2  -- upstream/pkgsrc_2012Q3

Now rebase newbranch ontp upstream/pkgsrc_2012Q3:

$ git rebase --onto upstream/pkgsrc_2012Q3 upstream/trunk newbranch

That means: take the changes that are in newbranch and are not in
upstream/trunk, and apply those changes to upstream/pkgsrc_2012Q3,
and call the result "newbranch".

So now you should have this:

  --A-------B-------C--D------------E------F--- origin/trunk
 /     /         /          /          /
--------------------------------------------- upstream/trunk
    \                          \
     -- upstream/pkgsrc_2012Q2  -- upstream/pkgsrc_2012Q3
                    \
                                     --A'--B'--C'--D'--E'-- newbranch

where A' to E' contian essentially the same changes as A to E.

I can't figure out how to edit comments, but there are some slashes and backslashes with the wrong amount of space before them, and some spelling mistakes.