How to revert last commits on branch, merge with other branch and re-add the commits?

Question

I have the following problem. A git repo was forked a while ago. Starting from this fork, changes were made, but at the same time the original repo was also modified a lot more even, somehow like this:

A-B-C-D-E master
   \[fork]
    C'-D'-E'-F'-G'-H'-I'-J'----X' remote/master

It is important to note that the fork basically decoupled master and remote/master. The problem now is, I can create a local branch from remote/master and merge it directly with the local master branch. However, this will bring up a lot of merge conflicts which I would like to avoid, because most of these conflicts are related to changes in the main software package before B. So what I eventually would need to do is to take the last few commits of master since the fork and put them on top of the remote/master branch. Is that possible?

Answer 1

If anyone comes to this question, I solved the issue by the following procedure:

• Created a new branch containing only all commits A-E and remove the latest commits C-E from the history of master:

  git checkout master
  git branch new_branch
  git reset --hard HEAD~5
  
      C-D-E new_branch
     /
  A-B       master
     \[fork]
      C'-D'-E'-F'-G'-H'-I'-J'----X' remote/master
  

• Merged the master branch with remote/master accepting all changes from remote/master:

  git checkout remote/master
  git merge -Xours master
  
      C-D-E new_branch
     /
  A-B---------------------------      
     \[fork]                    \
      C'-D'-E'-F'-G'-H'-I'-J'----X' remote/master, master
  

• Checked-out master and performed a rebase with remote/master

  git checkout master
  git rebase remote/master
  
  A-B---------------------------      
     \[fork]                    \
      C'-D'-E'-F'-G'-H'-I'-J'----X' remote/master, master
                                  \
                                   C-D-E new_branch