Add checkbox to delete pull branch after successful merge (#16049)

* Add checkbox to delete pull branch after successful merge

* Omit DeleteBranchAfterMerge field in json

* Log a warning instead of error when PR head branch deleted

* Add DefaultDeleteBranchAfterMerge to PullRequestConfig

* Add support for delete_branch_after_merge via API

* Fix for API: the branch should be deleted from the HEAD repo

If head and base repo are the same, reuse the already opened ctx.Repo.GitRepo

* Don't delegate to CleanupBranch, only reuse branch deletion code

CleanupBranch contains too much logic that has already been performed by the Merge

* Reuse gitrepo in MergePullRequest

Co-authored-by: Andrew Thornton <art27@cantab.net>

2 files changed, 46 insertions, 8 deletions

diff --git a/routers/api/v1/repo/pull.go b/routers/api/v1/repo/pull.go
index 0c09a9a86b..66bcabfd38 100644
--- a/routers/api/v1/repo/pull.go
+++ b/routers/api/v1/repo/pull.go
@@ -5,6 +5,7 @@
 package repo
 
 import (
+	"errors"
 	"fmt"
 	"math"
 	"net/http"
@@ -25,6 +26,7 @@ import (
 	"code.gitea.io/gitea/services/forms"
 	issue_service "code.gitea.io/gitea/services/issue"
 	pull_service "code.gitea.io/gitea/services/pull"
+	repo_service "code.gitea.io/gitea/services/repository"
 )
 
 // ListPullRequests returns a list of all PRs
@@ -878,6 +880,38 @@ func MergePullRequest(ctx *context.APIContext) {
 	}
 
 	log.Trace("Pull request merged: %d", pr.ID)
+
+	if form.DeleteBranchAfterMerge {
+		var headRepo *git.Repository
+		if ctx.Repo != nil && ctx.Repo.Repository != nil && ctx.Repo.Repository.ID == pr.HeadRepoID && ctx.Repo.GitRepo != nil {
+			headRepo = ctx.Repo.GitRepo
+		} else {
+			headRepo, err = git.OpenRepository(pr.HeadRepo.RepoPath())
+			if err != nil {
+				ctx.ServerError(fmt.Sprintf("OpenRepository[%s]", pr.HeadRepo.RepoPath()), err)
+				return
+			}
+			defer headRepo.Close()
+		}
+		if err := repo_service.DeleteBranch(ctx.User, pr.HeadRepo, headRepo, pr.HeadBranch); err != nil {
+			switch {
+			case git.IsErrBranchNotExist(err):
+				ctx.NotFound(err)
+			case errors.Is(err, repo_service.ErrBranchIsDefault):
+				ctx.Error(http.StatusForbidden, "DefaultBranch", fmt.Errorf("can not delete default branch"))
+			case errors.Is(err, repo_service.ErrBranchIsProtected):
+				ctx.Error(http.StatusForbidden, "IsProtectedBranch", fmt.Errorf("branch protected"))
+			default:
+				ctx.Error(http.StatusInternalServerError, "DeleteBranch", err)
+			}
+			return
+		}
+		if err := models.AddDeletePRBranchComment(ctx.User, pr.BaseRepo, pr.Issue.ID, pr.HeadBranch); err != nil {
+			// Do not fail here as branch has already been deleted
+			log.Error("DeleteBranch: %v", err)
+		}
+	}
+
 	ctx.Status(http.StatusOK)
 }
 
diff --git a/routers/api/v1/repo/repo.go b/routers/api/v1/repo/repo.go
index 5d397191a6..77691b4d15 100644
--- a/routers/api/v1/repo/repo.go
+++ b/routers/api/v1/repo/repo.go
@@ -833,14 +833,15 @@ func updateRepoUnits(ctx *context.APIContext, opts api.EditRepoOption) error {
 			if err != nil {
 				// Unit type doesn't exist so we make a new config file with default values
 				config = &models.PullRequestsConfig{
-					IgnoreWhitespaceConflicts: false,
-					AllowMerge:                true,
-					AllowRebase:               true,
-					AllowRebaseMerge:          true,
-					AllowSquash:               true,
-					AllowManualMerge:          true,
-					AutodetectManualMerge:     false,
-					DefaultMergeStyle:         models.MergeStyleMerge,
+					IgnoreWhitespaceConflicts:     false,
+					AllowMerge:                    true,
+					AllowRebase:                   true,
+					AllowRebaseMerge:              true,
+					AllowSquash:                   true,
+					AllowManualMerge:              true,
+					AutodetectManualMerge:         false,
+					DefaultDeleteBranchAfterMerge: false,
+					DefaultMergeStyle:             models.MergeStyleMerge,
 				}
 			} else {
 				config = unit.PullRequestsConfig()
@@ -867,6 +868,9 @@ func updateRepoUnits(ctx *context.APIContext, opts api.EditRepoOption) error {
 			if opts.AutodetectManualMerge != nil {
 				config.AutodetectManualMerge = *opts.AutodetectManualMerge
 			}
+			if opts.DefaultDeleteBranchAfterMerge != nil {
+				config.DefaultDeleteBranchAfterMerge = *opts.DefaultDeleteBranchAfterMerge
+			}
 			if opts.DefaultMergeStyle != nil {
 				config.DefaultMergeStyle = models.MergeStyle(*opts.DefaultMergeStyle)
 			}