Summary

While a Pull Request is open, if a source branch is manually rebased from and then merged with the target branch, and the target branch is subsequently pushed upstream, then the upstream server will show the pre-rebased commit on the source branch, but the post-rebased commit on the target branch. (This part is expected behaviour.)

If the rebased commit is then pushed to the source branch, instead of rescoping the Pull Request with the status of MERGED, the Pull Request is rescoped as DECLINED, even though the two branches now show identical commit histories

Steps to Reproduce

1. Create a new repo in BbS, clone the empty repo to your workstation, and create two commits on master:

   echo "test1" >> test.txt
   git add test.txt
   git commit -m "First commit"
   echo "test2" >> test.txt
   git add test.txt
   git commit -m "Second commit"
   git push origin master
   

1. Create a new branch, newbranch, that branches from "First commit" (i.e. it contains the first commit, but not the second)

   git checkout -b newbranch master~1
   echo "branchtest" >> newfile.txt
   git add .
   git commit -m "First branch commit"
   git push origin newbranch
   

1. Create a Pull Request from newbranch --> master
2. Rebase master onto newbranch then merge newbranch into master, and push those changes

   git rebase master
   git checkout master
   git merge newbranch
   git push origin
   

1. At this stage, newbranch contains the pre-rebase version of "First branch commit", and master contains the post-rebase version of the commit. The open PR has an empty diff, but it remains open as newbranch contains a commit hash that isn't present in the history of master. To rectify this, we now force push the rebased version of newbranch upsteam:

   git checkout newbranch
   git push -f origin newbranch
   

Expected behaviour:

After pushing the rebased version of newbranch upstream, the Pull Request is rescoped with the status of Merged, as newbranch and master now contain identical commit histories

Actual behaviour:

The Pull Request is rescoped with the status of Declined, although both branches now reflect identical commit histories