From 1608f63e396c78bcbea3605b812556ddf441a6c4 Mon Sep 17 00:00:00 2001
From: Mario Lubenka <mario.lubenka@googlemail.com>
Date: Wed, 12 Jun 2019 01:32:08 +0200
Subject: [PATCH] Fixes diff on merged pull requests (#7171)

---
 models/pull.go              |  2 +-
 modules/git/repo_compare.go |  8 ++++----
 routers/repo/pull.go        | 16 ++++++++--------
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/models/pull.go b/models/pull.go
index 5ac1126314..1f03dd9b0f 100644
--- a/models/pull.go
+++ b/models/pull.go
@@ -1144,7 +1144,7 @@ func (pr *PullRequest) UpdatePatch() (err error) {
 	defer func() {
 		headGitRepo.RemoveRemote(tmpRemote)
 	}()
-	pr.MergeBase, err = headGitRepo.GetMergeBase(tmpRemote, pr.BaseBranch, pr.HeadBranch)
+	pr.MergeBase, _, err = headGitRepo.GetMergeBase(tmpRemote, pr.BaseBranch, pr.HeadBranch)
 	if err != nil {
 		return fmt.Errorf("GetMergeBase: %v", err)
 	} else if err = pr.Update(); err != nil {
diff --git a/modules/git/repo_compare.go b/modules/git/repo_compare.go
index e7a1d72a85..42f0b9ad0c 100644
--- a/modules/git/repo_compare.go
+++ b/modules/git/repo_compare.go
@@ -22,8 +22,8 @@ type CompareInfo struct {
 	NumFiles  int
 }
 
-// GetMergeBase checks and returns merge base of two branches.
-func (repo *Repository) GetMergeBase(tmpRemote string, base, head string) (string, error) {
+// GetMergeBase checks and returns merge base of two branches and the reference used as base.
+func (repo *Repository) GetMergeBase(tmpRemote string, base, head string) (string, string, error) {
 	if tmpRemote == "" {
 		tmpRemote = "origin"
 	}
@@ -38,7 +38,7 @@ func (repo *Repository) GetMergeBase(tmpRemote string, base, head string) (strin
 	}
 
 	stdout, err := NewCommand("merge-base", base, head).RunInDir(repo.Path)
-	return strings.TrimSpace(stdout), err
+	return strings.TrimSpace(stdout), base, err
 }
 
 // GetCompareInfo generates and returns compare information between base and head branches of repositories.
@@ -59,7 +59,7 @@ func (repo *Repository) GetCompareInfo(basePath, baseBranch, headBranch string)
 	}
 
 	compareInfo := new(CompareInfo)
-	compareInfo.MergeBase, err = repo.GetMergeBase(tmpRemote, baseBranch, headBranch)
+	compareInfo.MergeBase, remoteBranch, err = repo.GetMergeBase(tmpRemote, baseBranch, headBranch)
 	if err == nil {
 		// We have a common base
 		logs, err := NewCommand("log", compareInfo.MergeBase+"..."+headBranch, prettyLogFormat).RunInDirBytes(repo.Path)
diff --git a/routers/repo/pull.go b/routers/repo/pull.go
index 182f715545..71c684356d 100644
--- a/routers/repo/pull.go
+++ b/routers/repo/pull.go
@@ -286,7 +286,7 @@ func PrepareMergedViewPullInfo(ctx *context.Context, issue *models.Issue) *git.C
 	setMergeTarget(ctx, pull)
 	ctx.Data["HasMerged"] = true
 
-	prInfo, err := ctx.Repo.GitRepo.GetCompareInfo(ctx.Repo.Repository.RepoPath(),
+	compareInfo, err := ctx.Repo.GitRepo.GetCompareInfo(ctx.Repo.Repository.RepoPath(),
 		pull.MergeBase, pull.GetGitRefName())
 
 	if err != nil {
@@ -301,9 +301,9 @@ func PrepareMergedViewPullInfo(ctx *context.Context, issue *models.Issue) *git.C
 		ctx.ServerError("GetCompareInfo", err)
 		return nil
 	}
-	ctx.Data["NumCommits"] = prInfo.Commits.Len()
-	ctx.Data["NumFiles"] = prInfo.NumFiles
-	return prInfo
+	ctx.Data["NumCommits"] = compareInfo.Commits.Len()
+	ctx.Data["NumFiles"] = compareInfo.NumFiles
+	return compareInfo
 }
 
 // PrepareViewPullInfo show meta information for a pull request preview page
@@ -336,7 +336,7 @@ func PrepareViewPullInfo(ctx *context.Context, issue *models.Issue) *git.Compare
 		return nil
 	}
 
-	prInfo, err := headGitRepo.GetCompareInfo(models.RepoPath(repo.Owner.Name, repo.Name),
+	compareInfo, err := headGitRepo.GetCompareInfo(models.RepoPath(repo.Owner.Name, repo.Name),
 		pull.BaseBranch, pull.HeadBranch)
 	if err != nil {
 		if strings.Contains(err.Error(), "fatal: Not a valid object name") {
@@ -361,9 +361,9 @@ func PrepareViewPullInfo(ctx *context.Context, issue *models.Issue) *git.Compare
 		ctx.Data["ConflictedFiles"] = pull.ConflictedFiles
 	}
 
-	ctx.Data["NumCommits"] = prInfo.Commits.Len()
-	ctx.Data["NumFiles"] = prInfo.NumFiles
-	return prInfo
+	ctx.Data["NumCommits"] = compareInfo.Commits.Len()
+	ctx.Data["NumFiles"] = compareInfo.NumFiles
+	return compareInfo
 }
 
 // ViewPullCommits show commits for a pull request