Branches not at ref commit ID should not be listed as Merged (#9614) (#9639)

Once a branch has been merged if the commit ID no longer equals that of
the pulls ref commit id don't offer to delete the branch on the pull screen
and don't list it as merged on branches.

Fix #9201

When looking at the pull page we should also get the commits from the refs/pulls/x/head

Fix #9158

3 files changed, 97 insertions, 31 deletions

diff --git a/routers/repo/branch.go b/routers/repo/branch.go
index 5d78518491..f57e76d494 100644
--- a/routers/repo/branch.go
+++ b/routers/repo/branch.go
@@ -16,6 +16,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/repofiles"
 	"code.gitea.io/gitea/modules/util"
+	"gopkg.in/src-d/go-git.v4/plumbing"
 )
 
 const (
@@ -32,6 +33,7 @@ type Branch struct {
 	CommitsAhead      int
 	CommitsBehind     int
 	LatestPullRequest *models.PullRequest
+	MergeMovedOn      bool
 }
 
 // Branches render repository branch page
@@ -168,6 +170,12 @@ func loadBranches(ctx *context.Context) []*Branch {
 		return nil
 	}
 
+	repoIDToRepo := map[int64]*models.Repository{}
+	repoIDToRepo[ctx.Repo.Repository.ID] = ctx.Repo.Repository
+
+	repoIDToGitRepo := map[int64]*git.Repository{}
+	repoIDToGitRepo[ctx.Repo.Repository.ID] = ctx.Repo.GitRepo
+
 	branches := make([]*Branch, len(rawBranches))
 	for i := range rawBranches {
 		commit, err := rawBranches[i].GetCommit()
@@ -196,11 +204,46 @@ func loadBranches(ctx *context.Context) []*Branch {
 			ctx.ServerError("GetLatestPullRequestByHeadInfo", err)
 			return nil
 		}
+		headCommit := commit.ID.String()
+
+		mergeMovedOn := false
 		if pr != nil {
+			pr.HeadRepo = ctx.Repo.Repository
 			if err := pr.LoadIssue(); err != nil {
 				ctx.ServerError("pr.LoadIssue", err)
 				return nil
 			}
+			if repo, ok := repoIDToRepo[pr.BaseRepoID]; ok {
+				pr.BaseRepo = repo
+			} else if err := pr.LoadBaseRepo(); err != nil {
+				ctx.ServerError("pr.LoadBaseRepo", err)
+				return nil
+			} else {
+				repoIDToRepo[pr.BaseRepoID] = pr.BaseRepo
+			}
+
+			if pr.HasMerged {
+				baseGitRepo, ok := repoIDToGitRepo[pr.BaseRepoID]
+				if !ok {
+					baseGitRepo, err = git.OpenRepository(pr.BaseRepo.RepoPath())
+					if err != nil {
+						ctx.ServerError("OpenRepository", err)
+						return nil
+					}
+					defer baseGitRepo.Close()
+					repoIDToGitRepo[pr.BaseRepoID] = baseGitRepo
+				}
+				pullCommit, err := baseGitRepo.GetRefCommitID(pr.GetGitRefName())
+				if err != nil && err != plumbing.ErrReferenceNotFound {
+					ctx.ServerError("GetBranchCommitID", err)
+					return nil
+				}
+				if err == nil && headCommit != pullCommit {
+					// the head has moved on from the merge - we shouldn't delete
+					mergeMovedOn = true
+				}
+			}
+
 		}
 
 		branches[i] = &Branch{
@@ -210,6 +253,7 @@ func loadBranches(ctx *context.Context) []*Branch {
 			CommitsAhead:      divergence.Ahead,
 			CommitsBehind:     divergence.Behind,
 			LatestPullRequest: pr,
+			MergeMovedOn:      mergeMovedOn,
 		}
 	}
 
diff --git a/routers/repo/issue.go b/routers/repo/issue.go
index 40e3b140ec..8cbad47f2d 100644
--- a/routers/repo/issue.go
+++ b/routers/repo/issue.go
@@ -931,7 +931,10 @@ func ViewIssue(ctx *context.Context) {
 			ctx.Data["IsBlockedByApprovals"] = pull.ProtectedBranch.RequiredApprovals > 0 && cnt < pull.ProtectedBranch.RequiredApprovals
 			ctx.Data["GrantedApprovals"] = cnt
 		}
-		ctx.Data["IsPullBranchDeletable"] = canDelete && pull.HeadRepo != nil && git.IsBranchExist(pull.HeadRepo.RepoPath(), pull.HeadBranch)
+		ctx.Data["IsPullBranchDeletable"] = canDelete &&
+			pull.HeadRepo != nil &&
+			git.IsBranchExist(pull.HeadRepo.RepoPath(), pull.HeadBranch) &&
+			(!pull.HasMerged || ctx.Data["HeadBranchCommitID"] == ctx.Data["PullHeadCommitID"])
 
 		ctx.Data["PullReviewersWithType"], err = models.GetReviewersByPullID(issue.ID)
 		if err != nil {
diff --git a/routers/repo/pull.go b/routers/repo/pull.go
index f46d093793..d3c17db4e7 100644
--- a/routers/repo/pull.go
+++ b/routers/repo/pull.go
@@ -315,25 +315,37 @@ func PrepareViewPullInfo(ctx *context.Context, issue *models.Issue) *git.Compare
 	repo := ctx.Repo.Repository
 	pull := issue.PullRequest
 
-	var err error
-	if err = pull.GetHeadRepo(); err != nil {
+	if err := pull.GetHeadRepo(); err != nil {
 		ctx.ServerError("GetHeadRepo", err)
 		return nil
 	}
 
+	if err := pull.GetBaseRepo(); err != nil {
+		ctx.ServerError("GetBaseRepo", err)
+		return nil
+	}
+
 	setMergeTarget(ctx, pull)
 
-	if err = pull.LoadProtectedBranch(); err != nil {
+	if err := pull.LoadProtectedBranch(); err != nil {
 		ctx.ServerError("GetLatestCommitStatus", err)
 		return nil
 	}
 	ctx.Data["EnableStatusCheck"] = pull.ProtectedBranch != nil && pull.ProtectedBranch.EnableStatusCheck
 
-	var headGitRepo *git.Repository
+	baseGitRepo, err := git.OpenRepository(pull.BaseRepo.RepoPath())
+	if err != nil {
+		ctx.ServerError("OpenRepository", err)
+		return nil
+	}
+	defer baseGitRepo.Close()
 	var headBranchExist bool
+	var headBranchSha string
 	// HeadRepo may be missing
 	if pull.HeadRepo != nil {
-		headGitRepo, err = git.OpenRepository(pull.HeadRepo.RepoPath())
+		var err error
+
+		headGitRepo, err := git.OpenRepository(pull.HeadRepo.RepoPath())
 		if err != nil {
 			ctx.ServerError("OpenRepository", err)
 			return nil
@@ -343,46 +355,53 @@ func PrepareViewPullInfo(ctx *context.Context, issue *models.Issue) *git.Compare
 		headBranchExist = headGitRepo.IsBranchExist(pull.HeadBranch)
 
 		if headBranchExist {
-			sha, err := headGitRepo.GetBranchCommitID(pull.HeadBranch)
+			headBranchSha, err = headGitRepo.GetBranchCommitID(pull.HeadBranch)
 			if err != nil {
 				ctx.ServerError("GetBranchCommitID", err)
 				return nil
 			}
+		}
+	}
 
-			commitStatuses, err := models.GetLatestCommitStatus(repo, sha, 0)
-			if err != nil {
-				ctx.ServerError("GetLatestCommitStatus", err)
-				return nil
-			}
-			if len(commitStatuses) > 0 {
-				ctx.Data["LatestCommitStatuses"] = commitStatuses
-				ctx.Data["LatestCommitStatus"] = models.CalcCommitStatus(commitStatuses)
-			}
+	sha, err := baseGitRepo.GetRefCommitID(pull.GetGitRefName())
+	if err != nil {
+		ctx.ServerError(fmt.Sprintf("GetRefCommitID(%s)", pull.GetGitRefName()), err)
+		return nil
+	}
 
-			if pull.ProtectedBranch != nil && pull.ProtectedBranch.EnableStatusCheck {
-				ctx.Data["is_context_required"] = func(context string) bool {
-					for _, c := range pull.ProtectedBranch.StatusCheckContexts {
-						if c == context {
-							return true
-						}
-					}
-					return false
+	commitStatuses, err := models.GetLatestCommitStatus(repo, sha, 0)
+	if err != nil {
+		ctx.ServerError("GetLatestCommitStatus", err)
+		return nil
+	}
+	if len(commitStatuses) > 0 {
+		ctx.Data["LatestCommitStatuses"] = commitStatuses
+		ctx.Data["LatestCommitStatus"] = models.CalcCommitStatus(commitStatuses)
+	}
+
+	if pull.ProtectedBranch != nil && pull.ProtectedBranch.EnableStatusCheck {
+		ctx.Data["is_context_required"] = func(context string) bool {
+			for _, c := range pull.ProtectedBranch.StatusCheckContexts {
+				if c == context {
+					return true
 				}
-				ctx.Data["IsRequiredStatusCheckSuccess"] = pull_service.IsCommitStatusContextSuccess(commitStatuses, pull.ProtectedBranch.StatusCheckContexts)
 			}
+			return false
 		}
+		ctx.Data["IsRequiredStatusCheckSuccess"] = pull_service.IsCommitStatusContextSuccess(commitStatuses, pull.ProtectedBranch.StatusCheckContexts)
 	}
 
-	if pull.HeadRepo == nil || !headBranchExist {
+	ctx.Data["HeadBranchMovedOn"] = headBranchSha != sha
+	ctx.Data["HeadBranchCommitID"] = headBranchSha
+	ctx.Data["PullHeadCommitID"] = sha
+
+	if pull.HeadRepo == nil || !headBranchExist || headBranchSha != sha {
 		ctx.Data["IsPullRequestBroken"] = true
 		ctx.Data["HeadTarget"] = "deleted"
-		ctx.Data["NumCommits"] = 0
-		ctx.Data["NumFiles"] = 0
-		return nil
 	}
 
-	compareInfo, err := headGitRepo.GetCompareInfo(models.RepoPath(repo.Owner.Name, repo.Name),
-		pull.BaseBranch, pull.HeadBranch)
+	compareInfo, err := baseGitRepo.GetCompareInfo(pull.BaseRepo.RepoPath(),
+		pull.BaseBranch, pull.GetGitRefName())
 	if err != nil {
 		if strings.Contains(err.Error(), "fatal: Not a valid object name") {
 			ctx.Data["IsPullRequestBroken"] = true