How to open GitHub PR for a proposed cherry-pick

Question

GitHub pull requests are all about merging two branches together:

• The "remote" branch, containing new changes you want to merge.
• The "local" branch you want to merge into, which GitHub calls the "base" branch.

Is there a way to create a branch that shows the same merge conflicts as a given cherry-pick, and that, when merged, is equivalent to performing that cherry-pick? In this instance we know the specific branch the cherry-pick will be applied to, if that makes any difference?

For example, is it sufficient to create a branch whose HEAD is the commit I want to cherry-pick, and open a PR for that branch?

Answer 1

A cherry-pick tries indeed to merge two patches together, but you will not be able to create a merge request on your work branch that does the same action as the cherry-pick.

---

Detailed view of a cherry-pick :

Here is my go at illustrating the merge operation performed by git cherry-pick :

Suppose you run git cherry-pick eacf32 from branch my/work :

# 'p' marks the parent commit of eacf32 :
---*-----*-----*------*-----* <- my/work
          \                   
           \               
            \-*---*----*----*-----*-----* <- some/other/branch
                       ^    ^
                       p   eacf32

# 'git cherry-pick eacf32' will try to resolve this merge :

                         my/work
                          v
---*-----* . . * . .* . . *----* <- would-be-cherry-pick
          \              /    /
           \            /    /
            \-*---*----*----* . . * . . *
                       ^    ^
                       p   eacf32

---

Turning it into an equivalent merge :

Following this diagram :

• you would want a branch cherrypick/target, with the actual content of my/work, grouped as one commit on top of p -- the parent commit of eacf32 :

  # start from your branch (you will have the expected content) :
  git checkout my/work
  # create a new branch and switch to it :
  git checkout -b cherrypick/target
  # use 'reset --soft' to move to the parent of eacf32
  # ('--soft' will keep all the differences as staged changes) :
  git reset --soft eacf32^
  # commit that :
  git commit
  

• you would want a branch cherrypick/source at eacf32 :

  git branch cherrypick/source eacf32
  

• you would merge cherrypick/source in cherrypick/target

---

What to do with the result of this merge ?

The possible merge conflicts and the content of the end result will be the same as the cherry-pick, you would obviously have to pick the content of that commit on top of your actual my/work branch.

As you can see from the diagram : the merge base for the cherry-pick must be p, so you won't be able to create a PR against your initial my/work branch, which gives the same result as the cherry-pick.