How to move certain commits to be based on another branch in git?

Question

The situation:

• master is at X
• quickfix1 is at X + 2 commits

Such that:

o-o-X (master HEAD)
     \
      q1a--q1b (quickfix1 HEAD)

Then I started working on quickfix2, but by accident took quickfix1 as the source branch to copy, not the master. Now quickfix2 is at X + 2 commits + 2 relevant commits.

o-o-X (master HEAD)
     \
      q1a--q1b (quickfix1 HEAD)
              \
               q2a--q2b (quickfix2 HEAD)

Now I want to have a branch with quickfix2, but without the 2 commits that belong to quickfix1.

      q2a'--q2b' (quickfix2 HEAD)
     /
o-o-X (master HEAD)
     \ 
      q1a--q1b (quickfix1 HEAD)

I tried to create a patch from a certain revision in quickfix2, but the patch doesn't preserve the commit history. Is there a way to save my commit history, but have a branch without changes in quickfix1?

Answer 1

This is a classic case of rebase --onto:

 # let's go to current master (X, where quickfix2 should begin)
 git checkout master

 # replay every commit *after* quickfix1 up to quickfix2 HEAD.
 git rebase --onto master quickfix1 quickfix2 

So you should go from

o-o-X (master HEAD)
     \ 
      q1a--q1b (quickfix1 HEAD)
              \
               q2a--q2b (quickfix2 HEAD)

to:

      q2a'--q2b' (new quickfix2 HEAD)
     /
o-o-X (master HEAD)
     \ 
      q1a--q1b (quickfix1 HEAD)

This is best done on a clean working tree.
See git config --global rebase.autostash true, especially after Git 2.10.