[API] Add pagination to ListBranches (#14524)

* make PaginateUserSlice generic -> PaginateSlice

* Add pagination to ListBranches

* add skip, limit to Repository.GetBranches()

* Move routers/api/v1/utils/utils PaginateSlice -> modules/util/paginate.go

* repo_module.GetBranches paginate

* fix & rename & more logging

* better description

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: a1012112796 <1012112796@qq.com>

5 files changed, 80 insertions, 24 deletions

diff --git a/modules/git/repo_branch.go b/modules/git/repo_branch.go
index 25438530f5..58781eb1c7 100644
--- a/modules/git/repo_branch.go
+++ b/modules/git/repo_branch.go
@@ -78,16 +78,17 @@ func (repo *Repository) GetBranch(branch string) (*Branch, error) {
 }
 
 // GetBranchesByPath returns a branch by it's path
-func GetBranchesByPath(path string) ([]*Branch, error) {
+// if limit = 0 it will not limit
+func GetBranchesByPath(path string, skip, limit int) ([]*Branch, int, error) {
 	gitRepo, err := OpenRepository(path)
 	if err != nil {
-		return nil, err
+		return nil, 0, err
 	}
 	defer gitRepo.Close()
 
-	brs, err := gitRepo.GetBranches()
+	brs, countAll, err := gitRepo.GetBranches(skip, limit)
 	if err != nil {
-		return nil, err
+		return nil, 0, err
 	}
 
 	branches := make([]*Branch, len(brs))
@@ -99,7 +100,7 @@ func GetBranchesByPath(path string) ([]*Branch, error) {
 		}
 	}
 
-	return branches, nil
+	return branches, countAll, nil
 }
 
 // DeleteBranchOptions Option(s) for delete branch
diff --git a/modules/git/repo_branch_gogit.go b/modules/git/repo_branch_gogit.go
index 65cb77a8b5..b00253f6ff 100644
--- a/modules/git/repo_branch_gogit.go
+++ b/modules/git/repo_branch_gogit.go
@@ -25,21 +25,32 @@ func (repo *Repository) IsBranchExist(name string) bool {
 	return reference.Type() != plumbing.InvalidReference
 }
 
-// GetBranches returns all branches of the repository.
-func (repo *Repository) GetBranches() ([]string, error) {
+// 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) {
 	var branchNames []string
 
 	branches, err := repo.gogitRepo.Branches()
 	if err != nil {
-		return nil, err
+		return nil, 0, err
 	}
 
+	i := 0
+	count := 0
 	_ = branches.ForEach(func(branch *plumbing.Reference) error {
+		count++
+		if i < skip {
+			i++
+			return nil
+		} else if limit != 0 && count > skip+limit {
+			return nil
+		}
+
 		branchNames = append(branchNames, strings.TrimPrefix(branch.Name().String(), BranchPrefix))
 		return nil
 	})
 
 	// TODO: Sort?
 
-	return branchNames, nil
+	return branchNames, count, nil
 }
diff --git a/modules/git/repo_branch_nogogit.go b/modules/git/repo_branch_nogogit.go
index 5ec46d725e..0628a57285 100644
--- a/modules/git/repo_branch_nogogit.go
+++ b/modules/git/repo_branch_nogogit.go
@@ -21,14 +21,14 @@ func (repo *Repository) IsBranchExist(name string) bool {
 	return IsReferenceExist(repo.Path, BranchPrefix+name)
 }
 
-// GetBranches returns all branches of the repository.
-func (repo *Repository) GetBranches() ([]string, error) {
-	return callShowRef(repo.Path, BranchPrefix, "--heads")
+// 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) {
+	return callShowRef(repo.Path, BranchPrefix, "--heads", skip, limit)
 }
 
-func callShowRef(repoPath, prefix, arg string) ([]string, error) {
-	var branchNames []string
-
+// callShowRef return refs, if limit = 0 it will not limit
+func callShowRef(repoPath, prefix, arg string, skip, limit int) (branchNames []string, countAll int, err error) {
 	stdoutReader, stdoutWriter := io.Pipe()
 	defer func() {
 		_ = stdoutReader.Close()
@@ -49,8 +49,21 @@ func callShowRef(repoPath, prefix, arg string) ([]string, error) {
 		}
 	}()
 
+	i := 0
 	bufReader := bufio.NewReader(stdoutReader)
-	for {
+	for i < skip {
+		_, isPrefix, err := bufReader.ReadLine()
+		if err == io.EOF {
+			return branchNames, i, nil
+		}
+		if err != nil {
+			return nil, 0, err
+		}
+		if !isPrefix {
+			i++
+		}
+	}
+	for limit == 0 || i < skip+limit {
 		// The output of show-ref is simply a list:
 		// <sha> SP <ref> LF
 		_, err := bufReader.ReadSlice(' ')
@@ -59,24 +72,39 @@ func callShowRef(repoPath, prefix, arg string) ([]string, error) {
 			_, err = bufReader.ReadSlice(' ')
 		}
 		if err == io.EOF {
-			return branchNames, nil
+			return branchNames, i, nil
 		}
 		if err != nil {
-			return nil, err
+			return nil, 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, nil
+			return branchNames, i, nil
 		}
 		if err != nil {
-			return nil, err
+			return nil, i, err
 		}
 		branchName = strings.TrimPrefix(branchName, prefix)
 		if len(branchName) > 0 {
 			branchName = branchName[:len(branchName)-1]
 		}
 		branchNames = append(branchNames, branchName)
+		i++
+	}
+	// count all refs
+	for limit != 0 {
+		_, isPrefix, err := bufReader.ReadLine()
+		if err == io.EOF {
+			return branchNames, i, nil
+		}
+		if err != nil {
+			return nil, 0, err
+		}
+		if !isPrefix {
+			i++
+		}
 	}
+	return branchNames, i, nil
 }
diff --git a/modules/git/repo_branch_test.go b/modules/git/repo_branch_test.go
index 33d31aef68..05d5237e6a 100644
--- a/modules/git/repo_branch_test.go
+++ b/modules/git/repo_branch_test.go
@@ -17,11 +17,26 @@ func TestRepository_GetBranches(t *testing.T) {
 	assert.NoError(t, err)
 	defer bareRepo1.Close()
 
-	branches, err := bareRepo1.GetBranches()
+	branches, countAll, err := bareRepo1.GetBranches(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)
 
 	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)
+
+	assert.NoError(t, err)
+	assert.Len(t, branches, 0)
+	assert.EqualValues(t, 3, countAll)
+	assert.ElementsMatch(t, []string{}, branches)
 }
 
 func BenchmarkRepository_GetBranches(b *testing.B) {
@@ -33,7 +48,7 @@ func BenchmarkRepository_GetBranches(b *testing.B) {
 	defer bareRepo1.Close()
 
 	for i := 0; i < b.N; i++ {
-		_, err := bareRepo1.GetBranches()
+		_, _, err := bareRepo1.GetBranches(0, 0)
 		if err != nil {
 			b.Fatal(err)
 		}
diff --git a/modules/git/repo_tag_nogogit.go b/modules/git/repo_tag_nogogit.go
index 83cbc58e34..b3fa5d6dc4 100644
--- a/modules/git/repo_tag_nogogit.go
+++ b/modules/git/repo_tag_nogogit.go
@@ -13,6 +13,7 @@ func (repo *Repository) IsTagExist(name string) bool {
 }
 
 // GetTags returns all tags of the repository.
-func (repo *Repository) GetTags() ([]string, error) {
-	return callShowRef(repo.Path, TagPrefix, "--tags")
+func (repo *Repository) GetTags() (tags []string, err error) {
+	tags, _, err = callShowRef(repo.Path, TagPrefix, "--tags", 0, 0)
+	return
 }