Refactor git command stdio pipe (#36422)

Most potential deadlock problems should have been fixed, and new code is
unlikely to cause new problems with the new design.

Also raise the minimum Git version required to 2.6.0 (released in 2015)

modules/git/attribute/batch.go

@@ -7,7 +7,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"os"
+	"io"
 	"path/filepath"
 	"time"
 
@@ -20,7 +20,7 @@ import (
 type BatchChecker struct {
 	attributesNum int
 	repo          *git.Repository
-	stdinWriter   *os.File
+	stdinWriter   io.WriteCloser
 	stdOut        *nulSeparatedAttributeWriter
 	ctx           context.Context
 	cancel        context.CancelFunc
@@ -60,10 +60,7 @@ func NewBatchChecker(repo *git.Repository, treeish string, attributes []string)
 		},
 	}
 
-	stdinReader, stdinWriter, err := os.Pipe()
-	if err != nil {
-		return nil, err
-	}
+	stdinWriter, stdinWriterClose := cmd.MakeStdinPipe()
 	checker.stdinWriter = stdinWriter
 
 	lw := new(nulSeparatedAttributeWriter)
@@ -71,21 +68,19 @@ func NewBatchChecker(repo *git.Repository, treeish string, attributes []string)
 	lw.closed = make(chan struct{})
 	checker.stdOut = lw
 
-	go func() {
-		defer func() {
-			_ = stdinReader.Close()
-			_ = lw.Close()
-		}()
-		err := cmd.WithEnv(envs).
-			WithDir(repo.Path).
-			WithStdin(stdinReader).
-			WithStdout(lw).
-			RunWithStderr(ctx)
+	cmd.WithEnv(envs).
+		WithDir(repo.Path).
+		WithStdoutCopy(lw)
 
+	go func() {
+		defer stdinWriterClose()
+		defer checker.cancel()
+		defer lw.Close()
+
+		err := cmd.RunWithStderr(ctx)
 		if err != nil && !gitcmd.IsErrorCanceledOrKilled(err) {
 			log.Error("Attribute checker for commit %s exits with error: %v", treeish, err)
 		}
-		checker.cancel()
 	}()
 
 	return checker, nil