From 272ae03341561ad51228fc75bd12ca3180504100 Mon Sep 17 00:00:00 2001
From: Giteabot <teabot@gitea.io>
Date: Fri, 8 Dec 2023 02:03:27 +0800
Subject: [PATCH] Make gogit Repository.GetBranchNames consistent (#28348)
 (#28386)

Backport #28348 by @AdamMajer

nogogit GetBranchNames() lists branches sorted in reverse commit date
order. On the other hand the gogit implementation doesn't apply any
ordering resulting in unpredictable behaviour. In my case, the unit
tests requiring particular order fail

    repo_branch_test.go:24:
                Error Trace:
               ./gitea/modules/git/repo_branch_test.go:24
                Error:          elements differ

                                extra elements in list A:
                                ([]interface {}) (len=1) {
                                 (string) (len=6) "master"
                                }

                                extra elements in list B:
                                ([]interface {}) (len=1) {
                                 (string) (len=7) "branch1"
                                }

                                listA:
                                ([]string) (len=2) {
                                 (string) (len=6) "master",
                                 (string) (len=7) "branch2"
                                }

                                listB:
                                ([]string) (len=2) {
                                 (string) (len=7) "branch1",
                                 (string) (len=7) "branch2"
                                }
                Test:           TestRepository_GetBranches

To fix this, we sort branches based on their commit date in gogit
implementation.

Fixes: #28318

Co-authored-by: Adam Majer <amajer@suse.de>
---
 modules/git/repo_branch_gogit.go | 41 ++++++++++++++++++++++----------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/modules/git/repo_branch_gogit.go b/modules/git/repo_branch_gogit.go
index f9896a7a09..1c0d9a18aa 100644
--- a/modules/git/repo_branch_gogit.go
+++ b/modules/git/repo_branch_gogit.go
@@ -8,6 +8,7 @@ package git
 
 import (
 	"context"
+	"sort"
 	"strings"
 
 	"github.com/go-git/go-git/v5/plumbing"
@@ -52,32 +53,46 @@ 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.
+// Branches are returned with sort of `-commiterdate` as the nogogit
+// implementation. This requires full fetch, sort and then the
+// skip/limit applies later as gogit returns in undefined order.
 func (repo *Repository) GetBranchNames(skip, limit int) ([]string, int, error) {
-	var branchNames []string
+	type BranchData struct {
+		name          string
+		committerDate int64
+	}
+	var branchData []BranchData
 
-	branches, err := repo.gogitRepo.Branches()
+	branchIter, err := repo.gogitRepo.Branches()
 	if err != nil {
 		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 {
+	_ = branchIter.ForEach(func(branch *plumbing.Reference) error {
+		obj, err := repo.gogitRepo.CommitObject(branch.Hash())
+		if err != nil {
+			// skip branch if can't find commit
 			return nil
 		}
 
-		branchNames = append(branchNames, strings.TrimPrefix(branch.Name().String(), BranchPrefix))
+		branchData = append(branchData, BranchData{strings.TrimPrefix(branch.Name().String(), BranchPrefix), obj.Committer.When.Unix()})
 		return nil
 	})
 
-	// TODO: Sort?
+	sort.Slice(branchData, func(i, j int) bool {
+		return !(branchData[i].committerDate < branchData[j].committerDate)
+	})
 
-	return branchNames, count, nil
+	var branchNames []string
+	maxPos := len(branchData)
+	if limit > 0 {
+		maxPos = min(skip+limit, maxPos)
+	}
+	for i := skip; i < maxPos; i++ {
+		branchNames = append(branchNames, branchData[i].name)
+	}
+
+	return branchNames, len(branchData), nil
 }
 
 // WalkReferences walks all the references from the repository