Add "Update Branch" button to Pull Requests (#9784)

* add Divergence

* add Update Button

* first working version

* re-use code

* split raw merge commands and db-change functions (notify, cache, ...)

* use rawMerge (remove redundant code)

* own function to get Diverging of PRs

* use FlashError

* correct Error Msg

* hook is triggerd ... so remove comment

* add "branch2" to "user2/repo1" because it unit-test "TestPullView_ReviewerMissed" use it but dont exist jet :/

* move GetPerm to IsUserAllowedToUpdate

* add Flash Success MSG

* imprufe code
- remove useless js chage

* fix-lint

* TEST: add PullRequest ID:5
Repo: user2/repo1
Base: branch1
Head: pr-to-update

* correct comments

* make PR5 outdated

* fix Tests

* WIP: add pull update test

* update revs

* update locales

* working TEST

* update UI

* misspell

* change style

* add 1s delay so rev exist

* move row up (before merge row)

* fix lint nit

* UI remove divider

* Update style

* nits

* do it right

* introduce IsSameRepo

* remove useless check

Co-authored-by: Lauris BH <lauris@nix.lv>

2 files changed, 180 insertions, 45 deletions

diff --git a/services/pull/merge.go b/services/pull/merge.go
index b423c663ea..26c9ab3d1c 100644
--- a/services/pull/merge.go
+++ b/services/pull/merge.go
@@ -33,11 +33,6 @@ import (
 // Caller should check PR is ready to be merged (review and status checks)
 // FIXME: add repoWorkingPull make sure two merges does not happen at same time.
 func Merge(pr *models.PullRequest, doer *models.User, baseGitRepo *git.Repository, mergeStyle models.MergeStyle, message string) (err error) {
-	binVersion, err := git.BinVersion()
-	if err != nil {
-		log.Error("git.BinVersion: %v", err)
-		return fmt.Errorf("Unable to get git version: %v", err)
-	}
 
 	if err = pr.GetHeadRepo(); err != nil {
 		log.Error("GetHeadRepo: %v", err)
@@ -63,6 +58,61 @@ func Merge(pr *models.PullRequest, doer *models.User, baseGitRepo *git.Repositor
 		go AddTestPullRequestTask(doer, pr.BaseRepo.ID, pr.BaseBranch, false, "", "")
 	}()
 
+	if err := rawMerge(pr, doer, mergeStyle, message); err != nil {
+		return err
+	}
+
+	pr.MergedCommitID, err = baseGitRepo.GetBranchCommitID(pr.BaseBranch)
+	if err != nil {
+		return fmt.Errorf("GetBranchCommit: %v", err)
+	}
+
+	pr.MergedUnix = timeutil.TimeStampNow()
+	pr.Merger = doer
+	pr.MergerID = doer.ID
+
+	if err = pr.SetMerged(); err != nil {
+		log.Error("setMerged [%d]: %v", pr.ID, err)
+	}
+
+	notification.NotifyMergePullRequest(pr, doer)
+
+	// Reset cached commit count
+	cache.Remove(pr.Issue.Repo.GetCommitsCountCacheKey(pr.BaseBranch, true))
+
+	// Resolve cross references
+	refs, err := pr.ResolveCrossReferences()
+	if err != nil {
+		log.Error("ResolveCrossReferences: %v", err)
+		return nil
+	}
+
+	for _, ref := range refs {
+		if err = ref.LoadIssue(); err != nil {
+			return err
+		}
+		if err = ref.Issue.LoadRepo(); err != nil {
+			return err
+		}
+		close := (ref.RefAction == references.XRefActionCloses)
+		if close != ref.Issue.IsClosed {
+			if err = issue_service.ChangeStatus(ref.Issue, doer, close); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+// rawMerge perform the merge operation without changing any pull information in database
+func rawMerge(pr *models.PullRequest, doer *models.User, mergeStyle models.MergeStyle, message string) (err error) {
+	binVersion, err := git.BinVersion()
+	if err != nil {
+		log.Error("git.BinVersion: %v", err)
+		return fmt.Errorf("Unable to get git version: %v", err)
+	}
+
 	// Clone base repo.
 	tmpBasePath, err := createTemporaryRepo(pr)
 	if err != nil {
@@ -337,46 +387,6 @@ func Merge(pr *models.PullRequest, doer *models.User, baseGitRepo *git.Repositor
 	outbuf.Reset()
 	errbuf.Reset()
 
-	pr.MergedCommitID, err = baseGitRepo.GetBranchCommitID(pr.BaseBranch)
-	if err != nil {
-		return fmt.Errorf("GetBranchCommit: %v", err)
-	}
-
-	pr.MergedUnix = timeutil.TimeStampNow()
-	pr.Merger = doer
-	pr.MergerID = doer.ID
-
-	if err = pr.SetMerged(); err != nil {
-		log.Error("setMerged [%d]: %v", pr.ID, err)
-	}
-
-	notification.NotifyMergePullRequest(pr, doer)
-
-	// Reset cached commit count
-	cache.Remove(pr.Issue.Repo.GetCommitsCountCacheKey(pr.BaseBranch, true))
-
-	// Resolve cross references
-	refs, err := pr.ResolveCrossReferences()
-	if err != nil {
-		log.Error("ResolveCrossReferences: %v", err)
-		return nil
-	}
-
-	for _, ref := range refs {
-		if err = ref.LoadIssue(); err != nil {
-			return err
-		}
-		if err = ref.Issue.LoadRepo(); err != nil {
-			return err
-		}
-		close := (ref.RefAction == references.XRefActionCloses)
-		if close != ref.Issue.IsClosed {
-			if err = issue_service.ChangeStatus(ref.Issue, doer, close); err != nil {
-				return err
-			}
-		}
-	}
-
 	return nil
 }
 
diff --git a/services/pull/update.go b/services/pull/update.go
new file mode 100644
index 0000000000..5f055827e1
--- /dev/null
+++ b/services/pull/update.go
@@ -0,0 +1,125 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package pull
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/log"
+)
+
+// Update updates pull request with base branch.
+func Update(pull *models.PullRequest, doer *models.User, message string) error {
+	//use merge functions but switch repo's and branch's
+	pr := &models.PullRequest{
+		HeadRepoID: pull.BaseRepoID,
+		BaseRepoID: pull.HeadRepoID,
+		HeadBranch: pull.BaseBranch,
+		BaseBranch: pull.HeadBranch,
+	}
+
+	if err := pr.LoadHeadRepo(); err != nil {
+		log.Error("LoadHeadRepo: %v", err)
+		return fmt.Errorf("LoadHeadRepo: %v", err)
+	} else if err = pr.LoadBaseRepo(); err != nil {
+		log.Error("LoadBaseRepo: %v", err)
+		return fmt.Errorf("LoadBaseRepo: %v", err)
+	}
+
+	diffCount, err := GetDiverging(pull)
+	if err != nil {
+		return err
+	} else if diffCount.Behind == 0 {
+		return fmt.Errorf("HeadBranch of PR %d is up to date", pull.Index)
+	}
+
+	defer func() {
+		go AddTestPullRequestTask(doer, pr.HeadRepo.ID, pr.HeadBranch, false, "", "")
+	}()
+
+	return rawMerge(pr, doer, models.MergeStyleMerge, message)
+}
+
+// IsUserAllowedToUpdate check if user is allowed to update PR with given permissions and branch protections
+func IsUserAllowedToUpdate(pull *models.PullRequest, user *models.User) (bool, error) {
+	headRepoPerm, err := models.GetUserRepoPermission(pull.HeadRepo, user)
+	if err != nil {
+		return false, err
+	}
+
+	pr := &models.PullRequest{
+		HeadRepoID: pull.BaseRepoID,
+		BaseRepoID: pull.HeadRepoID,
+		HeadBranch: pull.BaseBranch,
+		BaseBranch: pull.HeadBranch,
+	}
+	return IsUserAllowedToMerge(pr, headRepoPerm, user)
+}
+
+// GetDiverging determines how many commits a PR is ahead or behind the PR base branch
+func GetDiverging(pr *models.PullRequest) (*git.DivergeObject, error) {
+	log.Trace("PushToBaseRepo[%d]: pushing commits to base repo '%s'", pr.BaseRepoID, pr.GetGitRefName())
+	if err := pr.LoadBaseRepo(); err != nil {
+		return nil, err
+	}
+	if err := pr.LoadHeadRepo(); err != nil {
+		return nil, err
+	}
+
+	headRepoPath := pr.HeadRepo.RepoPath()
+	headGitRepo, err := git.OpenRepository(headRepoPath)
+	if err != nil {
+		return nil, fmt.Errorf("OpenRepository: %v", err)
+	}
+	defer headGitRepo.Close()
+
+	if pr.IsSameRepo() {
+		diff, err := git.GetDivergingCommits(pr.HeadRepo.RepoPath(), pr.BaseBranch, pr.HeadBranch)
+		return &diff, err
+	}
+
+	tmpRemoteName := fmt.Sprintf("tmp-pull-%d-base", pr.ID)
+	if err = headGitRepo.AddRemote(tmpRemoteName, pr.BaseRepo.RepoPath(), true); err != nil {
+		return nil, fmt.Errorf("headGitRepo.AddRemote: %v", err)
+	}
+	// Make sure to remove the remote even if the push fails
+	defer func() {
+		if err := headGitRepo.RemoveRemote(tmpRemoteName); err != nil {
+			log.Error("CountDiverging: RemoveRemote: %s", err)
+		}
+	}()
+
+	// $(git rev-list --count tmp-pull-1-base/master..feature) commits ahead of master
+	ahead, errorAhead := checkDivergence(headRepoPath, fmt.Sprintf("%s/%s", tmpRemoteName, pr.BaseBranch), pr.HeadBranch)
+	if errorAhead != nil {
+		return &git.DivergeObject{}, errorAhead
+	}
+
+	// $(git rev-list --count feature..tmp-pull-1-base/master) commits behind master
+	behind, errorBehind := checkDivergence(headRepoPath, pr.HeadBranch, fmt.Sprintf("%s/%s", tmpRemoteName, pr.BaseBranch))
+	if errorBehind != nil {
+		return &git.DivergeObject{}, errorBehind
+	}
+
+	return &git.DivergeObject{Ahead: ahead, Behind: behind}, nil
+}
+
+func checkDivergence(repoPath string, baseBranch string, targetBranch string) (int, error) {
+	branches := fmt.Sprintf("%s..%s", baseBranch, targetBranch)
+	cmd := git.NewCommand("rev-list", "--count", branches)
+	stdout, err := cmd.RunInDir(repoPath)
+	if err != nil {
+		return -1, err
+	}
+	outInteger, errInteger := strconv.Atoi(strings.Trim(stdout, "\n"))
+	if errInteger != nil {
+		return -1, errInteger
+	}
+	return outInteger, nil
+}