1 files changed, 37 insertions, 0 deletions

diff --git a/services/pull/pull.go b/services/pull/pull.go
index d1630f3792..930954bdfd 100644
--- a/services/pull/pull.go
+++ b/services/pull/pull.go
@@ -546,6 +546,43 @@ func (errs errlist) Error() string {
 	return ""
 }
 
+// RetargetChildrenOnMerge retarget children pull requests on merge if possible
+func RetargetChildrenOnMerge(ctx context.Context, doer *user_model.User, pr *issues_model.PullRequest) error {
+	if setting.Repository.PullRequest.RetargetChildrenOnMerge && pr.BaseRepoID == pr.HeadRepoID {
+		return RetargetBranchPulls(ctx, doer, pr.HeadRepoID, pr.HeadBranch, pr.BaseBranch)
+	}
+	return nil
+}
+
+// RetargetBranchPulls change target branch for all pull requests whose base branch is the branch
+// Both branch and targetBranch must be in the same repo (for security reasons)
+func RetargetBranchPulls(ctx context.Context, doer *user_model.User, repoID int64, branch, targetBranch string) error {
+	prs, err := issues_model.GetUnmergedPullRequestsByBaseInfo(ctx, repoID, branch)
+	if err != nil {
+		return err
+	}
+
+	if err := issues_model.PullRequestList(prs).LoadAttributes(ctx); err != nil {
+		return err
+	}
+
+	var errs errlist
+	for _, pr := range prs {
+		if err = pr.Issue.LoadRepo(ctx); err != nil {
+			errs = append(errs, err)
+		} else if err = ChangeTargetBranch(ctx, pr, doer, targetBranch); err != nil &&
+			!issues_model.IsErrIssueIsClosed(err) && !models.IsErrPullRequestHasMerged(err) &&
+			!issues_model.IsErrPullRequestAlreadyExists(err) {
+			errs = append(errs, err)
+		}
+	}
+
+	if len(errs) > 0 {
+		return errs
+	}
+	return nil
+}
+
 // CloseBranchPulls close all the pull requests who's head branch is the branch
 func CloseBranchPulls(ctx context.Context, doer *user_model.User, repoID int64, branch string) error {
 	prs, err := issues_model.GetUnmergedPullRequestsByHeadInfo(ctx, repoID, branch)