Refactor git command stdio pipe (#36393)

And remove the incorrect `ensureValidGitRepository`

modules/git/catfile_batch_test.go

@@ -6,6 +6,7 @@ package git
 import (
 	"io"
 	"path/filepath"
+	"sync"
 	"testing"
 
 	"code.gitea.io/gitea/modules/test"
@@ -25,7 +26,14 @@ func TestCatFileBatch(t *testing.T) {
 func testCatFileBatch(t *testing.T) {
 	t.Run("CorruptedGitRepo", func(t *testing.T) {
 		tmpDir := t.TempDir()
-		_, err := NewBatch(t.Context(), tmpDir)
+		batch, err := NewBatch(t.Context(), tmpDir)
+		// as long as the directory exists, no error, because we can't really know whether the git repo is valid until we run commands
+		require.NoError(t, err)
+		defer batch.Close()
+
+		_, err = batch.QueryInfo("e2129701f1a4d54dc44f03c93bca0a2aec7c5449")
+		require.Error(t, err)
+		_, err = batch.QueryInfo("e2129701f1a4d54dc44f03c93bca0a2aec7c5449")
 		require.Error(t, err)
 	})
 
@@ -52,4 +60,30 @@ func testCatFileBatch(t *testing.T) {
 		require.NoError(t, err)
 		require.Equal(t, "file1\n", string(content))
 	})
+
+	t.Run("QueryTerminated", func(t *testing.T) {
+		var c *catFileBatchCommunicator
+		switch b := batch.(type) {
+		case *catFileBatchLegacy:
+			c = b.batchCheck
+			_, _ = c.writer.Write([]byte("in-complete-line-"))
+		case *catFileBatchCommand:
+			c = b.batch
+			_, _ = c.writer.Write([]byte("info"))
+		default:
+			t.FailNow()
+			return
+		}
+
+		wg := sync.WaitGroup{}
+		wg.Go(func() {
+			buf := make([]byte, 100)
+			_, _ = c.reader.Read(buf)
+			n, errRead := c.reader.Read(buf)
+			assert.Zero(t, n)
+			assert.ErrorIs(t, errRead, io.EOF) // the pipe is closed due to command being killed
+		})
+		c.debugGitCmd.DebugKill()
+		wg.Wait()
+	})
 }