diff --git a/README.md b/README.md
index 582ac7bee9d..19e8920cd88 100644
--- a/README.md
+++ b/README.md
@@ -104,6 +104,7 @@ There are 5 ways to install Gogs:
 - [OpenShift](https://github.com/tkisme/gogs-openshift)
 - [Cloudron](https://cloudron.io/appstore.html#io.gogs.cloudronapp)
 - [Scaleway](https://www.scaleway.com/imagehub/gogs/)
+- [Portal](https://portaldemo.xyz/cloud/)
 
 ## Acknowledgments
 
diff --git a/gogs.go b/gogs.go
index c11111a2694..fe379aa23a0 100644
--- a/gogs.go
+++ b/gogs.go
@@ -17,7 +17,7 @@ import (
 	"github.com/gogits/gogs/modules/setting"
 )
 
-const APP_VER = "0.6.16.1002 Beta"
+const APP_VER = "0.6.16.1004 Beta"
 
 func init() {
 	runtime.GOMAXPROCS(runtime.NumCPU())
diff --git a/models/issue.go b/models/issue.go
index 2bc25da447c..0dd0b66370e 100644
--- a/models/issue.go
+++ b/models/issue.go
@@ -930,10 +930,12 @@ type PullRequest struct {
 	Merger         *User `xorm:"-"`
 }
 
+// Note: don't try to get Pull because will end up recursive querying.
 func (pr *PullRequest) AfterSet(colName string, _ xorm.Cell) {
 	var err error
 	switch colName {
 	case "head_repo_id":
+		// FIXME: shouldn't show error if it's known that head repository has been removed.
 		pr.HeadRepo, err = GetRepositoryByID(pr.HeadRepoID)
 		if err != nil {
 			log.Error(3, "GetRepositoryByID[%d]: %v", pr.ID, err)
@@ -1017,7 +1019,7 @@ func (pr *PullRequest) Merge(doer *User, baseGitRepo *git.Repository) (err error
 	if _, stderr, err = process.ExecDir(-1, tmpBasePath,
 		fmt.Sprintf("PullRequest.Merge(git pull): %s", tmpBasePath),
 		"git", "pull", headRepoPath, pr.HeadBarcnh); err != nil {
-		return fmt.Errorf("git pull: %s", stderr)
+		return fmt.Errorf("git pull[%s / %s -> %s]: %s", headRepoPath, pr.HeadBarcnh, tmpBasePath, stderr)
 	}
 
 	// Push back to upstream.
@@ -1059,27 +1061,32 @@ func NewPullRequest(repo *Repository, pull *Issue, labelIDs []int64, uuids []str
 	}
 
 	// Test apply patch.
+	if err = repo.UpdateLocalCopy(); err != nil {
+		return fmt.Errorf("UpdateLocalCopy: %v", err)
+	}
+
 	repoPath, err := repo.RepoPath()
 	if err != nil {
 		return fmt.Errorf("RepoPath: %v", err)
 	}
-	patchPath := path.Join(repoPath, "pulls", com.ToStr(pr.ID)+".patch")
+	patchPath := path.Join(repoPath, "pulls", com.ToStr(pull.ID)+".patch")
 
 	os.MkdirAll(path.Dir(patchPath), os.ModePerm)
 	if err = ioutil.WriteFile(patchPath, patch, 0644); err != nil {
 		return fmt.Errorf("save patch: %v", err)
 	}
-	defer os.Remove(patchPath)
 
-	stdout, stderr, err := process.ExecDir(-1, repoPath,
+	pr.CanAutoMerge = true
+	_, stderr, err := process.ExecDir(-1, repo.LocalCopyPath(),
 		fmt.Sprintf("NewPullRequest(git apply --check): %d", repo.ID),
-		"git", "apply", "--check", "-v", patchPath)
+		"git", "apply", "--check", patchPath)
 	if err != nil {
-		if strings.Contains(stderr, "fatal:") {
+		if strings.Contains(stderr, "patch does not apply") {
+			pr.CanAutoMerge = false
+		} else {
 			return fmt.Errorf("git apply --check: %v - %s", err, stderr)
 		}
 	}
-	pr.CanAutoMerge = !strings.Contains(stdout, "error: patch failed:")
 
 	pr.PullID = pull.ID
 	pr.PullIndex = pull.Index
diff --git a/models/repo.go b/models/repo.go
index d70454fc1c2..31e3660ae71 100644
--- a/models/repo.go
+++ b/models/repo.go
@@ -296,6 +296,35 @@ func (repo *Repository) DescriptionHtml() template.HTML {
 	return template.HTML(DescPattern.ReplaceAllStringFunc(base.Sanitizer.Sanitize(repo.Description), sanitize))
 }
 
+func (repo *Repository) LocalCopyPath() string {
+	return path.Join(setting.RepoRootPath, "local", com.ToStr(repo.ID))
+}
+
+// UpdateLocalCopy makes sure the local copy of repository is up-to-date.
+func (repo *Repository) UpdateLocalCopy() error {
+	repoPath, err := repo.RepoPath()
+	if err != nil {
+		return err
+	}
+
+	localPath := repo.LocalCopyPath()
+	if !com.IsExist(localPath) {
+		_, stderr, err := process.Exec(
+			fmt.Sprintf("UpdateLocalCopy(git clone): %s", repoPath), "git", "clone", repoPath, localPath)
+		if err != nil {
+			return fmt.Errorf("git clone: %v - %s", err, stderr)
+		}
+	} else {
+		_, stderr, err := process.ExecDir(-1, localPath,
+			fmt.Sprintf("UpdateLocalCopy(git pull): %s", repoPath), "git", "pull")
+		if err != nil {
+			return fmt.Errorf("git pull: %v - %s", err, stderr)
+		}
+	}
+
+	return nil
+}
+
 func isRepositoryExist(e Engine, u *User, repoName string) (bool, error) {
 	has, err := e.Get(&Repository{
 		OwnerID:   u.Id,
diff --git a/modules/git/repo_pull.go b/modules/git/repo_pull.go
index add32df9085..a9cc33a1d41 100644
--- a/modules/git/repo_pull.go
+++ b/modules/git/repo_pull.go
@@ -44,7 +44,7 @@ func (repo *Repository) GetPullRequestInfo(basePath, baseBranch, headBranch stri
 	}
 	prInfo.MergeBase = strings.TrimSpace(stdout)
 
-	stdout, stderr, err = com.ExecCmdDir(repo.Path, "git", "log", remoteBranch+"..."+headBranch, prettyLogFormat)
+	stdout, stderr, err = com.ExecCmdDir(repo.Path, "git", "log", prInfo.MergeBase+"..."+headBranch, prettyLogFormat)
 	if err != nil {
 		return nil, fmt.Errorf("list diff logs: %v", concatenateError(err, stderr))
 	}
@@ -64,20 +64,8 @@ func (repo *Repository) GetPullRequestInfo(basePath, baseBranch, headBranch stri
 }
 
 // GetPatch generates and returns patch data between given branches.
-func (repo *Repository) GetPatch(basePath, baseBranch, headBranch string) ([]byte, error) {
-	// Add a temporary remote.
-	tmpRemote := com.ToStr(time.Now().UnixNano())
-	_, stderr, err := com.ExecCmdDirBytes(repo.Path, "git", "remote", "add", "-f", tmpRemote, basePath)
-	if err != nil {
-		return nil, fmt.Errorf("add base as remote: %v", concatenateError(err, string(stderr)))
-	}
-	defer func() {
-		com.ExecCmdDir(repo.Path, "git", "remote", "remove", tmpRemote)
-	}()
-
-	var stdout []byte
-	remoteBranch := "remotes/" + tmpRemote + "/" + baseBranch
-	stdout, stderr, err = com.ExecCmdDirBytes(repo.Path, "git", "diff", "-p", remoteBranch, headBranch)
+func (repo *Repository) GetPatch(mergeBase, headBranch string) ([]byte, error) {
+	stdout, stderr, err := com.ExecCmdDirBytes(repo.Path, "git", "diff", "-p", mergeBase, headBranch)
 	if err != nil {
 		return nil, concatenateError(err, string(stderr))
 	}
diff --git a/routers/repo/pull.go b/routers/repo/pull.go
index c1eec7cc2f5..40c83351ca8 100644
--- a/routers/repo/pull.go
+++ b/routers/repo/pull.go
@@ -187,16 +187,22 @@ func PrepareViewPullInfo(ctx *middleware.Context, pull *models.Issue) *git.PullR
 	ctx.Data["HeadTarget"] = pull.HeadUserName + "/" + pull.HeadBarcnh
 	ctx.Data["BaseTarget"] = ctx.Repo.Owner.Name + "/" + pull.BaseBranch
 
-	headRepoPath, err := pull.HeadRepo.RepoPath()
-	if err != nil {
-		ctx.Handle(500, "HeadRepo.RepoPath", err)
-		return nil
-	}
+	var (
+		headGitRepo *git.Repository
+		err         error
+	)
+	if pull.HeadRepo != nil {
+		headRepoPath, err := pull.HeadRepo.RepoPath()
+		if err != nil {
+			ctx.Handle(500, "HeadRepo.RepoPath", err)
+			return nil
+		}
 
-	headGitRepo, err := git.OpenRepository(headRepoPath)
-	if err != nil {
-		ctx.Handle(500, "OpenRepository", err)
-		return nil
+		headGitRepo, err = git.OpenRepository(headRepoPath)
+		if err != nil {
+			ctx.Handle(500, "OpenRepository", err)
+			return nil
+		}
 	}
 
 	if pull.HeadRepo == nil || !headGitRepo.IsBranchExist(pull.HeadBarcnh) {
@@ -530,18 +536,18 @@ func CompareAndPullRequest(ctx *middleware.Context) {
 		return
 	}
 
-	pr, err := models.GetUnmergedPullRequest(headRepo.ID, ctx.Repo.Repository.ID, headBranch, baseBranch)
-	if err != nil {
-		if !models.IsErrPullRequestNotExist(err) {
-			ctx.Handle(500, "GetUnmergedPullRequest", err)
-			return
-		}
-	} else {
-		ctx.Data["HasPullRequest"] = true
-		ctx.Data["PullRequest"] = pr
-		ctx.HTML(200, COMPARE_PULL)
-		return
-	}
+	// pr, err := models.GetUnmergedPullRequest(headRepo.ID, ctx.Repo.Repository.ID, headBranch, baseBranch)
+	// if err != nil {
+	// 	if !models.IsErrPullRequestNotExist(err) {
+	// 		ctx.Handle(500, "GetUnmergedPullRequest", err)
+	// 		return
+	// 	}
+	// } else {
+	// 	ctx.Data["HasPullRequest"] = true
+	// 	ctx.Data["PullRequest"] = pr
+	// 	ctx.HTML(200, COMPARE_PULL)
+	// 	return
+	// }
 
 	nothingToCompare := PrepareCompareDiff(ctx, headUser, headRepo, headGitRepo, prInfo, baseBranch, headBranch)
 	if ctx.Written() {
@@ -575,7 +581,7 @@ func CompareAndPullRequestPost(ctx *middleware.Context, form auth.CreateIssueFor
 		return
 	}
 
-	patch, err := headGitRepo.GetPatch(models.RepoPath(repo.Owner.Name, repo.Name), baseBranch, headBranch)
+	patch, err := headGitRepo.GetPatch(prInfo.MergeBase, headBranch)
 	if err != nil {
 		ctx.Handle(500, "GetPatch", err)
 		return
diff --git a/templates/.VERSION b/templates/.VERSION
index 96127f4a46d..79f6fe8a178 100644
--- a/templates/.VERSION
+++ b/templates/.VERSION
@@ -1 +1 @@
-0.6.16.1002 Beta
\ No newline at end of file
+0.6.16.1004 Beta
\ No newline at end of file