Improve checkBranchName (go-gitea#17901)

The current implementation of checkBranchName is highly inefficient
involving opening the repository, the listing all of the branch names
checking them individually before then using using opened repo to get
the tags.

This PR avoids this by simply walking the references from show-ref
instead of opening the repository (in the nogogit case).

Signed-off-by: Andrew Thornton <art27@cantab.net>

modules/context/repo.go

@@ -584,7 +584,7 @@ func RepoAssignment(ctx *Context) (cancel context.CancelFunc) {
 	}
 	ctx.Data["Tags"] = tags
 
-	brs, _, err := ctx.Repo.GitRepo.GetBranches(0, 0)
+	brs, _, err := ctx.Repo.GitRepo.GetBranchNames(0, 0)
 	if err != nil {
 		ctx.ServerError("GetBranches", err)
 		return
@@ -810,7 +810,7 @@ func RepoRefByType(refType RepoRefType, ignoreNotExistErr ...bool) func(*Context
 		if len(ctx.Params("*")) == 0 {
 			refName = ctx.Repo.Repository.DefaultBranch
 			if !ctx.Repo.GitRepo.IsBranchExist(refName) {
-				brs, _, err := ctx.Repo.GitRepo.GetBranches(0, 0)
+				brs, _, err := ctx.Repo.GitRepo.GetBranchNames(0, 0)
 				if err != nil {
 					ctx.ServerError("GetBranches", err)
 					return

modules/git/repo_branch.go

@@ -95,17 +95,22 @@ func GetBranchesByPath(path string, skip, limit int) ([]*Branch, int, error) {
 	}
 	defer gitRepo.Close()
 
-	brs, countAll, err := gitRepo.GetBranches(skip, limit)
+	return gitRepo.GetBranches(skip, limit)
+}
+
+// GetBranches returns a slice of *git.Branch
+func (repo *Repository) GetBranches(skip, limit int) ([]*Branch, int, error) {
+	brs, countAll, err := repo.GetBranchNames(skip, limit)
 	if err != nil {
 		return nil, 0, err
 	}
 
 	branches := make([]*Branch, len(brs))
 	for i := range brs {
 		branches[i] = &Branch{
-			Path:    path,
+			Path:    repo.Path,
 			Name:    brs[i],
-			gitRepo: gitRepo,
+			gitRepo: repo,
 		}
 	}
 

modules/git/repo_branch_gogit.go

@@ -9,6 +9,7 @@
 package git
 
 import (
+	"context"
 	"strings"
 
 	"github.com/go-git/go-git/v5/plumbing"
@@ -52,7 +53,7 @@ func (repo *Repository) IsBranchExist(name string) bool {
 
 // GetBranches returns branches from the repository, skipping skip initial branches and
 // returning at most limit branches, or all branches if limit is 0.
-func (repo *Repository) GetBranches(skip, limit int) ([]string, int, error) {
+func (repo *Repository) GetBranchNames(skip, limit int) ([]string, int, error) {
 	var branchNames []string
 
 	branches, err := repo.gogitRepo.Branches()
@@ -79,3 +80,26 @@ func (repo *Repository) GetBranches(skip, limit int) ([]string, int, error) {
 
 	return branchNames, count, nil
 }
+
+// WalkReferences walks all the references from the repository
+func WalkReferences(ctx context.Context, repoPath string, walkfn func(string) error) (int, error) {
+	repo, err := OpenRepositoryCtx(ctx, repoPath)
+	if err != nil {
+		return 0, err
+	}
+	defer repo.Close()
+
+	i := 0
+	iter, err := repo.gogitRepo.References()
+	if err != nil {
+		return i, err
+	}
+	defer iter.Close()
+
+	err = iter.ForEach(func(ref *plumbing.Reference) error {
+		err := walkfn(string(ref.Name()))
+		i++
+		return err
+	})
+	return i, err
+}

modules/git/repo_branch_nogogit.go

@@ -61,14 +61,29 @@ func (repo *Repository) IsBranchExist(name string) bool {
 	return repo.IsReferenceExist(BranchPrefix + name)
 }
 
-// GetBranches returns branches from the repository, skipping skip initial branches and
+// GetBranchNames returns branches from the repository, skipping skip initial branches and
 // returning at most limit branches, or all branches if limit is 0.
-func (repo *Repository) GetBranches(skip, limit int) ([]string, int, error) {
+func (repo *Repository) GetBranchNames(skip, limit int) ([]string, int, error) {
 	return callShowRef(repo.Ctx, repo.Path, BranchPrefix, "--heads", skip, limit)
 }
 
+// WalkReferences walks all the references from the repository
+func WalkReferences(ctx context.Context, repoPath string, walkfn func(string) error) (int, error) {
+	return walkShowRef(ctx, repoPath, "", 0, 0, walkfn)
+}
+
 // callShowRef return refs, if limit = 0 it will not limit
 func callShowRef(ctx context.Context, repoPath, prefix, arg string, skip, limit int) (branchNames []string, countAll int, err error) {
+	countAll, err = walkShowRef(ctx, repoPath, arg, skip, limit, func(branchName string) error {
+		branchName = strings.TrimPrefix(branchName, prefix)
+		branchNames = append(branchNames, branchName)
+
+		return nil
+	})
+	return
+}
+
+func walkShowRef(ctx context.Context, repoPath, arg string, skip, limit int, walkfn func(string) error) (countAll int, err error) {
 	stdoutReader, stdoutWriter := io.Pipe()
 	defer func() {
 		_ = stdoutReader.Close()
@@ -77,7 +92,11 @@ func callShowRef(ctx context.Context, repoPath, prefix, arg string, skip, limit
 
 	go func() {
 		stderrBuilder := &strings.Builder{}
-		err := NewCommandContext(ctx, "show-ref", arg).RunInDirPipeline(repoPath, stdoutWriter, stderrBuilder)
+		args := []string{"show-ref"}
+		if arg != "" {
+			args = append(args, arg)
+		}
+		err := NewCommandContext(ctx, args...).RunInDirPipeline(repoPath, stdoutWriter, stderrBuilder)
 		if err != nil {
 			if stderrBuilder.Len() == 0 {
 				_ = stdoutWriter.Close()
@@ -94,10 +113,10 @@ func callShowRef(ctx context.Context, repoPath, prefix, arg string, skip, limit
 	for i < skip {
 		_, isPrefix, err := bufReader.ReadLine()
 		if err == io.EOF {
-			return branchNames, i, nil
+			return i, nil
 		}
 		if err != nil {
-			return nil, 0, err
+			return 0, err
 		}
 		if !isPrefix {
 			i++
@@ -112,39 +131,42 @@ func callShowRef(ctx context.Context, repoPath, prefix, arg string, skip, limit
 			_, err = bufReader.ReadSlice(' ')
 		}
 		if err == io.EOF {
-			return branchNames, i, nil
+			return i, nil
 		}
 		if err != nil {
-			return nil, 0, err
+			return 0, err
 		}
 
 		branchName, err := bufReader.ReadString('\n')
 		if err == io.EOF {
 			// This shouldn't happen... but we'll tolerate it for the sake of peace
-			return branchNames, i, nil
+			return i, nil
 		}
 		if err != nil {
-			return nil, i, err
+			return i, err
 		}
-		branchName = strings.TrimPrefix(branchName, prefix)
+
 		if len(branchName) > 0 {
 			branchName = branchName[:len(branchName)-1]
 		}
-		branchNames = append(branchNames, branchName)
+		err = walkfn(branchName)
+		if err != nil {
+			return i, err
+		}
 		i++
 	}
 	// count all refs
 	for limit != 0 {
 		_, isPrefix, err := bufReader.ReadLine()
 		if err == io.EOF {
-			return branchNames, i, nil
+			return i, nil
 		}
 		if err != nil {
-			return nil, 0, err
+			return 0, err
 		}
 		if !isPrefix {
 			i++
 		}
 	}
-	return branchNames, i, nil
+	return i, nil
 }

modules/git/repo_branch_test.go

@@ -17,21 +17,21 @@ func TestRepository_GetBranches(t *testing.T) {
 	assert.NoError(t, err)
 	defer bareRepo1.Close()
 
-	branches, countAll, err := bareRepo1.GetBranches(0, 2)
+	branches, countAll, err := bareRepo1.GetBranchNames(0, 2)
 
 	assert.NoError(t, err)
 	assert.Len(t, branches, 2)
 	assert.EqualValues(t, 3, countAll)
 	assert.ElementsMatch(t, []string{"branch1", "branch2"}, branches)
 
-	branches, countAll, err = bareRepo1.GetBranches(0, 0)
+	branches, countAll, err = bareRepo1.GetBranchNames(0, 0)
 
 	assert.NoError(t, err)
 	assert.Len(t, branches, 3)
 	assert.EqualValues(t, 3, countAll)
 	assert.ElementsMatch(t, []string{"branch1", "branch2", "master"}, branches)
 
-	branches, countAll, err = bareRepo1.GetBranches(5, 1)
+	branches, countAll, err = bareRepo1.GetBranchNames(5, 1)
 
 	assert.NoError(t, err)
 	assert.Len(t, branches, 0)
@@ -48,7 +48,7 @@ func BenchmarkRepository_GetBranches(b *testing.B) {
 	defer bareRepo1.Close()
 
 	for i := 0; i < b.N; i++ {
-		_, _, err := bareRepo1.GetBranches(0, 0)
+		_, _, err := bareRepo1.GetBranchNames(0, 0)
 		if err != nil {
 			b.Fatal(err)
 		}

routers/web/repo/branch.go

@@ -165,14 +165,14 @@ func redirect(ctx *context.Context) {
 // loadBranches loads branches from the repository limited by page & pageSize.
 // NOTE: May write to context on error.
 func loadBranches(ctx *context.Context, skip, limit int) ([]*Branch, int) {
-	defaultBranch, err := repo_service.GetBranch(ctx.Repo.Repository, ctx.Repo.Repository.DefaultBranch)
+	defaultBranch, err := ctx.Repo.GitRepo.GetBranch(ctx.Repo.Repository.DefaultBranch)
 	if err != nil {
 		log.Error("loadBranches: get default branch: %v", err)
 		ctx.ServerError("GetDefaultBranch", err)
 		return nil, 0
 	}
 
-	rawBranches, totalNumOfBranches, err := repo_service.GetBranches(ctx.Repo.Repository, skip, limit)
+	rawBranches, totalNumOfBranches, err := ctx.Repo.GitRepo.GetBranches(skip, limit)
 	if err != nil {
 		log.Error("GetBranches: %v", err)
 		ctx.ServerError("GetBranches", err)

routers/web/repo/compare.go

@@ -660,7 +660,7 @@ func getBranchesAndTagsForRepo(repo *models.Repository) (branches, tags []string
 	}
 	defer gitRepo.Close()
 
-	branches, _, err = gitRepo.GetBranches(0, 0)
+	branches, _, err = gitRepo.GetBranchNames(0, 0)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -711,7 +711,7 @@ func CompareDiff(ctx *context.Context) {
 		return
 	}
 
-	headBranches, _, err := ci.HeadGitRepo.GetBranches(0, 0)
+	headBranches, _, err := ci.HeadGitRepo.GetBranchNames(0, 0)
 	if err != nil {
 		ctx.ServerError("GetBranches", err)
 		return

routers/web/repo/issue.go

@@ -690,7 +690,7 @@ func RetrieveRepoMetas(ctx *context.Context, repo *models.Repository, isPull boo
 		return nil
 	}
 
-	brs, _, err := ctx.Repo.GitRepo.GetBranches(0, 0)
+	brs, _, err := ctx.Repo.GitRepo.GetBranchNames(0, 0)
 	if err != nil {
 		ctx.ServerError("GetBranches", err)
 		return nil

services/repository/adopt.go

@@ -142,7 +142,7 @@ func adoptRepository(ctx context.Context, repoPath string, u *user_model.User, r
 
 		repo.DefaultBranch = strings.TrimPrefix(repo.DefaultBranch, git.BranchPrefix)
 	}
-	branches, _, _ := gitRepo.GetBranches(0, 0)
+	branches, _, _ := gitRepo.GetBranchNames(0, 0)
 	found := false
 	hasDefault := false
 	hasMaster := false

services/repository/branch.go

@@ -5,8 +5,10 @@
 package repository
 
 import (
+	"context"
 	"errors"
 	"fmt"
+	"strings"
 
 	"code.gitea.io/gitea/models"
 	user_model "code.gitea.io/gitea/models/user"
@@ -20,7 +22,7 @@ import (
 // CreateNewBranch creates a new repository branch
 func CreateNewBranch(doer *user_model.User, repo *models.Repository, oldBranchName, branchName string) (err error) {
 	// Check if branch name can be used
-	if err := checkBranchName(repo, branchName); err != nil {
+	if err := checkBranchName(git.DefaultContext, repo, branchName); err != nil {
 		return err
 	}
 
@@ -65,44 +67,39 @@ func GetBranches(repo *models.Repository, skip, limit int) ([]*git.Branch, int,
 }
 
 // checkBranchName validates branch name with existing repository branches
-func checkBranchName(repo *models.Repository, name string) error {
-	gitRepo, err := git.OpenRepository(repo.RepoPath())
-	if err != nil {
-		return err
-	}
-	defer gitRepo.Close()
-
-	branches, _, err := GetBranches(repo, 0, 0)
-	if err != nil {
-		return err
-	}
-
-	for _, branch := range branches {
-		if branch.Name == name {
+func checkBranchName(ctx context.Context, repo *models.Repository, name string) error {
+	_, err := git.WalkReferences(ctx, repo.RepoPath(), func(refName string) error {
+		branchRefName := strings.TrimPrefix(refName, git.BranchPrefix)
+		switch {
+		case branchRefName == name:
 			return models.ErrBranchAlreadyExists{
-				BranchName: branch.Name,
+				BranchName: name,
 			}
-		} else if (len(branch.Name) < len(name) && branch.Name+"/" == name[0:len(branch.Name)+1]) ||
-			(len(branch.Name) > len(name) && name+"/" == branch.Name[0:len(name)+1]) {
+		// If branchRefName like a/b but we want to create a branch named a then we have a conflict
+		case strings.HasPrefix(branchRefName, name+"/"):
 			return models.ErrBranchNameConflict{
-				BranchName: branch.Name,
+				BranchName: branchRefName,
+			}
+			// Conversely if branchRefName like a but we want to create a branch named a/b then we also have a conflict
+		case strings.HasPrefix(name, branchRefName+"/"):
+			return models.ErrBranchNameConflict{
+				BranchName: branchRefName,
+			}
+		case refName == git.TagPrefix+name:
+			return models.ErrTagAlreadyExists{
+				TagName: name,
 			}
 		}
-	}
-
-	if _, err := gitRepo.GetTag(name); err == nil {
-		return models.ErrTagAlreadyExists{
-			TagName: name,
-		}
-	}
+		return nil
+	})
 
-	return nil
+	return err
 }
 
 // CreateNewBranchFromCommit creates a new repository branch
 func CreateNewBranchFromCommit(doer *user_model.User, repo *models.Repository, commit, branchName string) (err error) {
 	// Check if branch name can be used
-	if err := checkBranchName(repo, branchName); err != nil {
+	if err := checkBranchName(git.DefaultContext, repo, branchName); err != nil {
 		return err
 	}