diff --git a/modules/git/repo_compare.go b/modules/git/repo_compare.go
index f60696a76378d..8d26f1e9e7304 100644
--- a/modules/git/repo_compare.go
+++ b/modules/git/repo_compare.go
@@ -18,32 +18,6 @@ import (
 	"code.gitea.io/gitea/modules/git/gitcmd"
 )
 
-// GetMergeBase checks and returns merge base of two branches and the reference used as base.
-func (repo *Repository) GetMergeBase(tmpRemote, base, head string) (string, string, error) {
-	if tmpRemote == "" {
-		tmpRemote = "origin"
-	}
-
-	if tmpRemote != "origin" {
-		tmpBaseName := RemotePrefix + tmpRemote + "/tmp_" + base
-		// Fetch commit into a temporary branch in order to be able to handle commits and tags
-		_, _, err := gitcmd.NewCommand("fetch", "--no-tags").
-			AddDynamicArguments(tmpRemote).
-			AddDashesAndList(base + ":" + tmpBaseName).
-			WithDir(repo.Path).
-			RunStdString(repo.Ctx)
-		if err == nil {
-			base = tmpBaseName
-		}
-	}
-
-	stdout, _, err := gitcmd.NewCommand("merge-base").
-		AddDashesAndList(base, head).
-		WithDir(repo.Path).
-		RunStdString(repo.Ctx)
-	return strings.TrimSpace(stdout), base, err
-}
-
 type lineCountWriter struct {
 	numLines int
 }
diff --git a/modules/gitrepo/fetch.go b/modules/gitrepo/fetch.go
new file mode 100644
index 0000000000000..53a4e044310c2
--- /dev/null
+++ b/modules/gitrepo/fetch.go
@@ -0,0 +1,19 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package gitrepo
+
+import (
+	"context"
+
+	"code.gitea.io/gitea/modules/git/gitcmd"
+)
+
+// FetchRemoteCommit fetches a specific commit and related commits from a remote repository into the managed repository
+// it will be checked in 2 weeks by default from git if the pull request created failure.
+// It's enough for a temporary fetch to get the merge base.
+func FetchRemoteCommit(ctx context.Context, repo, remoteRepo Repository, commitID string) error {
+	return RunCmd(ctx, repo, gitcmd.NewCommand("fetch", "--no-tags").
+		AddDynamicArguments(repoPath(remoteRepo)).
+		AddDynamicArguments(commitID))
+}
diff --git a/modules/gitrepo/gitrepo.go b/modules/gitrepo/gitrepo.go
index 3a9b0a1c8980b..4ad08d73de886 100644
--- a/modules/gitrepo/gitrepo.go
+++ b/modules/gitrepo/gitrepo.go
@@ -118,3 +118,8 @@ func CreateRepoFile(ctx context.Context, repo Repository, relativeFilePath strin
 	absoluteFilePath := filepath.Join(repoPath(repo), relativeFilePath)
 	return os.Create(absoluteFilePath)
 }
+
+func MkRepoDir(ctx context.Context, repo Repository, relativeDirPath string) error {
+	absoluteDirPath := filepath.Join(repoPath(repo), relativeDirPath)
+	return os.MkdirAll(absoluteDirPath, os.ModePerm)
+}
diff --git a/modules/gitrepo/merge.go b/modules/gitrepo/merge.go
new file mode 100644
index 0000000000000..2d83a1eb2ba4b
--- /dev/null
+++ b/modules/gitrepo/merge.go
@@ -0,0 +1,34 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package gitrepo
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"code.gitea.io/gitea/modules/git/gitcmd"
+)
+
+// MergeBase checks and returns merge base of two commits.
+func MergeBase(ctx context.Context, repo Repository, baseCommitID, headCommitID string) (string, error) {
+	mergeBase, err := RunCmdString(ctx, repo, gitcmd.NewCommand("merge-base").
+		AddDashesAndList(baseCommitID, headCommitID))
+	if err != nil {
+		return "", fmt.Errorf("get merge-base of %s and %s failed: %w", baseCommitID, headCommitID, err)
+	}
+	return strings.TrimSpace(mergeBase), nil
+}
+
+// MergeBaseFromRemote checks and returns merge base of two commits from different repositories.
+func MergeBaseFromRemote(ctx context.Context, baseRepo, headRepo Repository, baseCommitID, headCommitID string) (string, error) {
+	// fetch head commit id into the current repository if the repositories are different
+	if baseRepo.RelativePath() != headRepo.RelativePath() {
+		if err := FetchRemoteCommit(ctx, baseRepo, headRepo, headCommitID); err != nil {
+			return "", fmt.Errorf("FetchRemoteCommit: %w", err)
+		}
+	}
+
+	return MergeBase(ctx, baseRepo, baseCommitID, headCommitID)
+}
diff --git a/services/asymkey/sign.go b/services/asymkey/sign.go
index d778ff8918be6..fb4157451aa34 100644
--- a/services/asymkey/sign.go
+++ b/services/asymkey/sign.go
@@ -346,7 +346,7 @@ Loop:
 				return false, nil, nil, &ErrWontSign{commitsSigned}
 			}
 			// need to work out merge-base
-			mergeBaseCommit, _, err := gitRepo.GetMergeBase("", baseCommit, headCommit)
+			mergeBaseCommit, err := gitrepo.MergeBaseFromRemote(ctx, pr.BaseRepo, pr.HeadRepo, baseCommit, headCommit)
 			if err != nil {
 				return false, nil, nil, err
 			}
diff --git a/services/issue/pull.go b/services/issue/pull.go
index 8ee14c0a4b5ae..50b40dd0df9d3 100644
--- a/services/issue/pull.go
+++ b/services/issue/pull.go
@@ -7,35 +7,16 @@ import (
 	"context"
 	"fmt"
 	"slices"
-	"time"
 
 	issues_model "code.gitea.io/gitea/models/issues"
 	org_model "code.gitea.io/gitea/models/organization"
-	repo_model "code.gitea.io/gitea/models/repo"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/gitrepo"
-	"code.gitea.io/gitea/modules/graceful"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 )
 
-func getMergeBase(ctx context.Context, repo *repo_model.Repository, gitRepo *git.Repository, pr *issues_model.PullRequest, baseBranch, headBranch string) (string, error) {
-	// Add a temporary remote
-	tmpRemote := fmt.Sprintf("mergebase-%d-%d", pr.ID, time.Now().UnixNano())
-	if err := gitrepo.GitRemoteAdd(ctx, repo, tmpRemote, gitRepo.Path); err != nil {
-		return "", fmt.Errorf("GitRemoteAdd: %w", err)
-	}
-	defer func() {
-		if err := gitrepo.GitRemoteRemove(graceful.GetManager().ShutdownContext(), repo, tmpRemote); err != nil {
-			log.Error("getMergeBase: GitRemoteRemove: %v", err)
-		}
-	}()
-
-	mergeBase, _, err := gitRepo.GetMergeBase(tmpRemote, baseBranch, headBranch)
-	return mergeBase, err
-}
-
 type ReviewRequestNotifier struct {
 	Comment    *issues_model.Comment
 	IsAdd      bool
@@ -99,14 +80,16 @@ func PullRequestCodeOwnersReview(ctx context.Context, pr *issues_model.PullReque
 	}
 
 	// get the mergebase
-	mergeBase, err := getMergeBase(ctx, pr.BaseRepo, repo, pr, git.BranchPrefix+pr.BaseBranch, pr.GetGitHeadRefName())
-	if err != nil {
-		return nil, err
+	if pr.MergeBase == "" {
+		mergeBase, err := gitrepo.MergeBaseFromRemote(ctx, pr.BaseRepo, pr.HeadRepo, git.BranchPrefix+pr.BaseBranch, pr.GetGitHeadRefName())
+		if err != nil {
+			return nil, err
+		}
+		pr.MergeBase = mergeBase
 	}
-
 	// https://github.com/go-gitea/gitea/issues/29763, we need to get the files changed
 	// between the merge base and the head commit but not the base branch and the head commit
-	changedFiles, err := repo.GetFilesChangedBetween(mergeBase, pr.GetGitHeadRefName())
+	changedFiles, err := repo.GetFilesChangedBetween(pr.MergeBase, pr.GetGitHeadRefName())
 	if err != nil {
 		return nil, err
 	}
diff --git a/services/migrations/gitea_uploader.go b/services/migrations/gitea_uploader.go
index 96c2655b3ab1e..b7b1631d8d363 100644
--- a/services/migrations/gitea_uploader.go
+++ b/services/migrations/gitea_uploader.go
@@ -8,8 +8,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"os"
-	"path/filepath"
 	"strconv"
 	"strings"
 	"time"
@@ -589,12 +587,11 @@ func (g *GiteaLocalUploader) updateGitForPullRequest(ctx context.Context, pr *ba
 		}
 		defer ret.Close()
 
-		pullDir := filepath.Join(g.repo.RepoPath(), "pulls")
-		if err = os.MkdirAll(pullDir, os.ModePerm); err != nil {
+		if err = gitrepo.MkRepoDir(ctx, g.repo, "pulls"); err != nil {
 			return err
 		}
 
-		f, err := os.Create(filepath.Join(pullDir, fmt.Sprintf("%d.patch", pr.Number)))
+		f, err := gitrepo.CreateRepoFile(ctx, g.repo, "pulls/"+fmt.Sprintf("%d.patch", pr.Number))
 		if err != nil {
 			return err
 		}
@@ -739,7 +736,7 @@ func (g *GiteaLocalUploader) newPullRequest(ctx context.Context, pr *base.PullRe
 		if pr.Base.Ref != "" && pr.Head.SHA != "" {
 			// A PR against a tag base does not make sense - therefore pr.Base.Ref must be a branch
 			// TODO: should we be checking for the refs/heads/ prefix on the pr.Base.Ref? (i.e. are these actually branches or refs)
-			pr.Base.SHA, _, err = g.gitRepo.GetMergeBase("", git.BranchPrefix+pr.Base.Ref, pr.Head.SHA)
+			pr.Base.SHA, err = gitrepo.MergeBase(ctx, g.repo, git.BranchPrefix+pr.Base.Ref, pr.Head.SHA)
 			if err != nil {
 				log.Error("Cannot determine the merge base for PR #%d in %s/%s. Error: %v", pr.Number, g.repoOwner, g.repoName, err)
 			}
diff --git a/services/pull/compare.go b/services/pull/compare.go
index fbdb17cfdd937..00a74f2972fc3 100644
--- a/services/pull/compare.go
+++ b/services/pull/compare.go
@@ -6,14 +6,10 @@ package pull
 import (
 	"context"
 	"fmt"
-	"strconv"
-	"time"
 
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/gitrepo"
-	"code.gitea.io/gitea/modules/graceful"
-	logger "code.gitea.io/gitea/modules/log"
 )
 
 // CompareInfo represents needed information for comparing references.
@@ -27,48 +23,29 @@ type CompareInfo struct {
 
 // GetCompareInfo generates and returns compare information between base and head branches of repositories.
 func GetCompareInfo(ctx context.Context, baseRepo, headRepo *repo_model.Repository, headGitRepo *git.Repository, baseBranch, headBranch string, directComparison, fileOnly bool) (_ *CompareInfo, err error) {
-	var (
-		remoteBranch string
-		tmpRemote    string
-	)
-
-	// We don't need a temporary remote for same repository.
-	if baseRepo.ID != headRepo.ID {
-		// Add a temporary remote
-		tmpRemote = strconv.FormatInt(time.Now().UnixNano(), 10)
-		if err = gitrepo.GitRemoteAdd(ctx, headRepo, tmpRemote, baseRepo.RepoPath()); err != nil {
-			return nil, fmt.Errorf("GitRemoteAdd: %w", err)
-		}
-		defer func() {
-			if err := gitrepo.GitRemoteRemove(graceful.GetManager().ShutdownContext(), headRepo, tmpRemote); err != nil {
-				logger.Error("GetPullRequestInfo: GitRemoteRemove: %v", err)
-			}
-		}()
-	}
-
 	compareInfo := new(CompareInfo)
 
 	compareInfo.HeadCommitID, err = gitrepo.GetFullCommitID(ctx, headRepo, headBranch)
 	if err != nil {
 		compareInfo.HeadCommitID = headBranch
 	}
+	compareInfo.BaseCommitID, err = gitrepo.GetFullCommitID(ctx, baseRepo, baseBranch)
+	if err != nil {
+		compareInfo.BaseCommitID = baseBranch
+	}
 
-	compareInfo.MergeBase, remoteBranch, err = headGitRepo.GetMergeBase(tmpRemote, baseBranch, headBranch)
+	compareInfo.MergeBase, err = gitrepo.MergeBaseFromRemote(ctx, baseRepo, headRepo, compareInfo.BaseCommitID, compareInfo.HeadCommitID)
 	if err == nil {
-		compareInfo.BaseCommitID, err = gitrepo.GetFullCommitID(ctx, headRepo, remoteBranch)
-		if err != nil {
-			compareInfo.BaseCommitID = remoteBranch
-		}
 		separator := "..."
-		baseCommitID := compareInfo.MergeBase
+		startCommitID := compareInfo.MergeBase
 		if directComparison {
 			separator = ".."
-			baseCommitID = compareInfo.BaseCommitID
+			startCommitID = compareInfo.BaseCommitID
 		}
 
 		// We have a common base - therefore we know that ... should work
 		if !fileOnly {
-			compareInfo.Commits, err = headGitRepo.ShowPrettyFormatLogToList(ctx, baseCommitID+separator+headBranch)
+			compareInfo.Commits, err = headGitRepo.ShowPrettyFormatLogToList(ctx, startCommitID+separator+headBranch)
 			if err != nil {
 				return nil, fmt.Errorf("ShowPrettyFormatLogToList: %w", err)
 			}
@@ -77,17 +54,13 @@ func GetCompareInfo(ctx context.Context, baseRepo, headRepo *repo_model.Reposito
 		}
 	} else {
 		compareInfo.Commits = []*git.Commit{}
-		compareInfo.MergeBase, err = gitrepo.GetFullCommitID(ctx, headRepo, remoteBranch)
-		if err != nil {
-			compareInfo.MergeBase = remoteBranch
-		}
-		compareInfo.BaseCommitID = compareInfo.MergeBase
+		compareInfo.MergeBase = compareInfo.BaseCommitID
 	}
 
 	// Count number of changed files.
 	// This probably should be removed as we need to use shortstat elsewhere
 	// Now there is git diff --shortstat but this appears to be slower than simply iterating with --nameonly
-	compareInfo.NumFiles, err = headGitRepo.GetDiffNumChangedFiles(remoteBranch, headBranch, directComparison)
+	compareInfo.NumFiles, err = headGitRepo.GetDiffNumChangedFiles(compareInfo.BaseCommitID, compareInfo.HeadCommitID, directComparison)
 	if err != nil {
 		return nil, err
 	}
diff --git a/services/pull/pull.go b/services/pull/pull.go
index ecc0b2c7cebce..165e2750210ee 100644
--- a/services/pull/pull.go
+++ b/services/pull/pull.go
@@ -510,14 +510,7 @@ func checkIfPRContentChanged(ctx context.Context, pr *issues_model.PullRequest,
 	}
 	defer cancel()
 
-	tmpRepo, err := git.OpenRepository(ctx, prCtx.tmpBasePath)
-	if err != nil {
-		return false, "", fmt.Errorf("OpenRepository: %w", err)
-	}
-	defer tmpRepo.Close()
-
-	// Find the merge-base
-	mergeBase, _, err = tmpRepo.GetMergeBase("", "base", "tracking")
+	mergeBase, err = gitrepo.MergeBaseFromRemote(ctx, pr.BaseRepo, pr.HeadRepo, pr.BaseBranch, pr.HeadBranch)
 	if err != nil {
 		return false, "", fmt.Errorf("GetMergeBase: %w", err)
 	}
diff --git a/services/repository/generate.go b/services/repository/generate.go
index b2913cd110fee..bc37bc7bfedf0 100644
--- a/services/repository/generate.go
+++ b/services/repository/generate.go
@@ -21,7 +21,6 @@ import (
 	git_model "code.gitea.io/gitea/models/git"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/modules/git"
-	"code.gitea.io/gitea/modules/git/gitcmd"
 	"code.gitea.io/gitea/modules/gitrepo"
 	"code.gitea.io/gitea/modules/glob"
 	"code.gitea.io/gitea/modules/log"
@@ -216,19 +215,6 @@ func processGiteaTemplateFile(ctx context.Context, tmpDir string, templateRepo,
 }
 
 func generateRepoCommit(ctx context.Context, repo, templateRepo, generateRepo *repo_model.Repository, tmpDir string) error {
-	commitTimeStr := time.Now().Format(time.RFC3339)
-	authorSig := repo.Owner.NewGitSig()
-
-	// Because this may call hooks we should pass in the environment
-	env := append(os.Environ(),
-		"GIT_AUTHOR_NAME="+authorSig.Name,
-		"GIT_AUTHOR_EMAIL="+authorSig.Email,
-		"GIT_AUTHOR_DATE="+commitTimeStr,
-		"GIT_COMMITTER_NAME="+authorSig.Name,
-		"GIT_COMMITTER_EMAIL="+authorSig.Email,
-		"GIT_COMMITTER_DATE="+commitTimeStr,
-	)
-
 	// Clone to temporary path and do the init commit.
 	if err := gitrepo.CloneRepoToLocal(ctx, templateRepo, tmpDir, git.CloneRepoOptions{
 		Depth:  1,
@@ -264,15 +250,6 @@ func generateRepoCommit(ctx context.Context, repo, templateRepo, generateRepo *r
 		return err
 	}
 
-	if stdout, _, err := gitcmd.NewCommand("remote", "add", "origin").
-		AddDynamicArguments(repo.RepoPath()).
-		WithDir(tmpDir).
-		WithEnv(env).
-		RunStdString(ctx); err != nil {
-		log.Error("Unable to add %v as remote origin to temporary repo to %s: stdout %s\nError: %v", repo, tmpDir, stdout, err)
-		return fmt.Errorf("git remote add: %w", err)
-	}
-
 	if err = git.AddTemplateSubmoduleIndexes(ctx, tmpDir, submodules); err != nil {
 		return fmt.Errorf("failed to add submodules: %v", err)
 	}
diff --git a/services/repository/init.go b/services/repository/init.go
index 51cc113d63ab9..8b9081b37ecb4 100644
--- a/services/repository/init.go
+++ b/services/repository/init.go
@@ -11,7 +11,9 @@ import (
 
 	repo_model "code.gitea.io/gitea/models/repo"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/git/gitcmd"
+	"code.gitea.io/gitea/modules/gitrepo"
 	"code.gitea.io/gitea/modules/log"
 	repo_module "code.gitea.io/gitea/modules/repository"
 	"code.gitea.io/gitea/modules/setting"
@@ -71,12 +73,11 @@ func initRepoCommit(ctx context.Context, tmpPath string, repo *repo_model.Reposi
 		defaultBranch = setting.Repository.DefaultBranch
 	}
 
-	if stdout, _, err := gitcmd.NewCommand("push", "origin").
-		AddDynamicArguments("HEAD:" + defaultBranch).
-		WithDir(tmpPath).
-		WithEnv(repo_module.InternalPushingEnvironment(u, repo)).
-		RunStdString(ctx); err != nil {
-		log.Error("Failed to push back to HEAD: Stdout: %s\nError: %v", stdout, err)
+	if err := gitrepo.PushFromLocal(ctx, tmpPath, repo, git.PushOptions{
+		Branch: defaultBranch,
+		Env:    repo_module.InternalPushingEnvironment(u, repo),
+	}); err != nil {
+		log.Error("Failed to push back to HEAD Error: %v", err)
 		return fmt.Errorf("git push: %w", err)
 	}