Git merge into past commit

Question

We have a git history that looks like this. This is already pushed to remote but can I possibly merge the branches at certain commits? Or am I limited to only merging the commit at the very top?

where blue is origin/master and magenta is a feature branch that has been physically copied into the master branch.

Answer 1

Assume the commit history as below, and you want to merge feature branch into commit B:

...---A---B---C---D  master

...---E---F---G---H  feature

Then you can execute below commands:

git checkout commitB
git merge feature --allow-unrelated-histories

Assume the merge commit id commit M as below commit history:

                  C---D  master
                 /
      ...---A---B---M 
                   /
...---E---F---G---H  feature

Then you can execute the commands:

git rebase --onto commitM commitB master
git push origin master -f

And now the commit history will be:

      ...---A---B---M---C'---D'  master 
                   /
...---E---F---G---H  feature

Answer 2

Being in the master branch then git merge "commit-id" This should do it