Refactor git command context & pipeline (#36406)

Less and simpler code, fewer bugs

services/pull/pull.go

@@ -8,7 +8,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"os"
 	"regexp"
 	"strings"
 	"time"
@@ -526,18 +525,11 @@ func checkIfPRContentChanged(ctx context.Context, pr *issues_model.PullRequest,
 	}
 
 	cmd := gitcmd.NewCommand("diff", "--name-only", "-z").AddDynamicArguments(newCommitID, oldCommitID, mergeBase)
-	stdoutReader, stdoutWriter, err := os.Pipe()
-	if err != nil {
-		return false, mergeBase, fmt.Errorf("unable to open pipe for to run diff: %w", err)
-	}
 
+	var stdoutReader io.ReadCloser
 	if err := cmd.WithDir(prCtx.tmpBasePath).
-		WithStdout(stdoutWriter).
-		WithPipelineFunc(func(ctx context.Context, cancel context.CancelFunc) error {
-			_ = stdoutWriter.Close()
-			defer func() {
-				_ = stdoutReader.Close()
-			}()
+		WithStdoutReader(&stdoutReader).
+		WithPipelineFunc(func(ctx gitcmd.Context) error {
 			return util.IsEmptyReader(stdoutReader)
 		}).
 		RunWithStderr(ctx); err != nil {