From b5406ec3e0b009efb8599dcef6a695cd0cbc3b89 Mon Sep 17 00:00:00 2001
From: Adam Majer <amajer@suse.de>
Date: Mon, 4 Dec 2023 17:31:54 +0100
Subject: [PATCH] Make gogit Repository.GetBranchNames consistent

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
---
 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 f9896a7a09047..1c0d9a18aa9d9 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)
+	})
+
+	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, count, nil
+	return branchNames, len(branchData), nil
 }
 
 // WalkReferences walks all the references from the repository