test: use `T.TempDir` to create temporary test directory (#21043)

A testing cleanup. 

This pull request replaces `os.MkdirTemp` with `t.TempDir`. We can use the `T.TempDir` function from the `testing` package to create temporary directory. The directory created by `T.TempDir` is automatically removed when the test and all its subtests complete. 

This saves us at least 2 lines (error check, and cleanup) on every instance, or in some cases adds cleanup that we forgot.

Reference: https://pkg.go.dev/testing#T.TempDir

```go
func TestFoo(t *testing.T) {
	// before
	tmpDir, err := os.MkdirTemp("", "")
	require.NoError(t, err)
	defer os.RemoveAll(tmpDir)

	// now
	tmpDir := t.TempDir()
}
```

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

1 files changed, 2 insertions, 6 deletions

diff --git a/modules/git/repo_compare_test.go b/modules/git/repo_compare_test.go
index 245920c2bd..63f7254dea 100644
--- a/modules/git/repo_compare_test.go
+++ b/modules/git/repo_compare_test.go
@@ -10,19 +10,16 @@ import (
 	"path/filepath"
 	"testing"
 
-	"code.gitea.io/gitea/modules/util"
-
 	"github.com/stretchr/testify/assert"
 )
 
 func TestGetFormatPatch(t *testing.T) {
 	bareRepo1Path := filepath.Join(testReposDir, "repo1_bare")
-	clonedPath, err := cloneRepo(bareRepo1Path, "repo1_TestGetFormatPatch")
+	clonedPath, err := cloneRepo(t, bareRepo1Path)
 	if err != nil {
 		assert.NoError(t, err)
 		return
 	}
-	defer util.RemoveAll(clonedPath)
 
 	repo, err := openRepositoryWithDefaultContext(clonedPath)
 	if err != nil {
@@ -84,12 +81,11 @@ func TestReadWritePullHead(t *testing.T) {
 	bareRepo1Path := filepath.Join(testReposDir, "repo1_bare")
 
 	// As we are writing we should clone the repository first
-	clonedPath, err := cloneRepo(bareRepo1Path, "TestReadWritePullHead")
+	clonedPath, err := cloneRepo(t, bareRepo1Path)
 	if err != nil {
 		assert.NoError(t, err)
 		return
 	}
-	defer util.RemoveAll(clonedPath)
 
 	repo, err := openRepositoryWithDefaultContext(clonedPath)
 	if err != nil {