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/pipeline/catfile.go

@@ -6,67 +6,33 @@ package pipeline
 import (
 	"bufio"
 	"context"
-	"fmt"
 	"io"
 	"strconv"
 	"strings"
-	"sync"
 
 	"code.gitea.io/gitea/modules/git/gitcmd"
 )
 
 // CatFileBatchCheck runs cat-file with --batch-check
-func CatFileBatchCheck(ctx context.Context, shasToCheckReader *io.PipeReader, catFileCheckWriter *io.PipeWriter, wg *sync.WaitGroup, tmpBasePath string) {
-	defer wg.Done()
-	defer shasToCheckReader.Close()
-	defer catFileCheckWriter.Close()
-
-	cmd := gitcmd.NewCommand("cat-file", "--batch-check")
-	if err := cmd.WithDir(tmpBasePath).
-		WithStdin(shasToCheckReader).
-		WithStdout(catFileCheckWriter).
-		RunWithStderr(ctx); err != nil {
-		_ = catFileCheckWriter.CloseWithError(fmt.Errorf("git cat-file --batch-check [%s]: %w", tmpBasePath, err))
-	}
+func CatFileBatchCheck(ctx context.Context, cmd *gitcmd.Command, tmpBasePath string) error {
+	cmd.AddArguments("cat-file", "--batch-check")
+	return cmd.WithDir(tmpBasePath).RunWithStderr(ctx)
 }
 
 // CatFileBatchCheckAllObjects runs cat-file with --batch-check --batch-all
-func CatFileBatchCheckAllObjects(ctx context.Context, catFileCheckWriter *io.PipeWriter, wg *sync.WaitGroup, tmpBasePath string, errChan chan<- error) {
-	defer wg.Done()
-	defer catFileCheckWriter.Close()
-
-	cmd := gitcmd.NewCommand("cat-file", "--batch-check", "--batch-all-objects")
-	if err := cmd.WithDir(tmpBasePath).
-		WithStdout(catFileCheckWriter).
-		RunWithStderr(ctx); err != nil {
-		_ = catFileCheckWriter.CloseWithError(fmt.Errorf("git cat-file --batch-check --batch-all-object [%s]: %w", tmpBasePath, err))
-		errChan <- err
-	}
+func CatFileBatchCheckAllObjects(ctx context.Context, cmd *gitcmd.Command, tmpBasePath string) error {
+	return cmd.AddArguments("cat-file", "--batch-check", "--batch-all-objects").WithDir(tmpBasePath).RunWithStderr(ctx)
 }
 
 // CatFileBatch runs cat-file --batch
-func CatFileBatch(ctx context.Context, shasToBatchReader *io.PipeReader, catFileBatchWriter *io.PipeWriter, wg *sync.WaitGroup, tmpBasePath string) {
-	defer wg.Done()
-	defer shasToBatchReader.Close()
-	defer catFileBatchWriter.Close()
-
-	if err := gitcmd.NewCommand("cat-file", "--batch").
-		WithDir(tmpBasePath).
-		WithStdin(shasToBatchReader).
-		WithStdout(catFileBatchWriter).
-		RunWithStderr(ctx); err != nil {
-		_ = shasToBatchReader.CloseWithError(fmt.Errorf("git rev-list [%s]: %w", tmpBasePath, err))
-	}
+func CatFileBatch(ctx context.Context, cmd *gitcmd.Command, tmpBasePath string) error {
+	return cmd.AddArguments("cat-file", "--batch").WithDir(tmpBasePath).RunWithStderr(ctx)
 }
 
 // BlobsLessThan1024FromCatFileBatchCheck reads a pipeline from cat-file --batch-check and returns the blobs <1024 in size
-func BlobsLessThan1024FromCatFileBatchCheck(catFileCheckReader *io.PipeReader, shasToBatchWriter *io.PipeWriter, wg *sync.WaitGroup) {
-	defer wg.Done()
-	defer catFileCheckReader.Close()
-	scanner := bufio.NewScanner(catFileCheckReader)
-	defer func() {
-		_ = shasToBatchWriter.CloseWithError(scanner.Err())
-	}()
+func BlobsLessThan1024FromCatFileBatchCheck(in io.ReadCloser, out io.WriteCloser) error {
+	defer out.Close()
+	scanner := bufio.NewScanner(in)
 	for scanner.Scan() {
 		line := scanner.Text()
 		if len(line) == 0 {
@@ -82,12 +48,12 @@ func BlobsLessThan1024FromCatFileBatchCheck(catFileCheckReader *io.PipeReader, s
 		}
 		toWrite := []byte(fields[0] + "\n")
 		for len(toWrite) > 0 {
-			n, err := shasToBatchWriter.Write(toWrite)
+			n, err := out.Write(toWrite)
 			if err != nil {
-				_ = catFileCheckReader.CloseWithError(err)
-				break
+				return err
 			}
 			toWrite = toWrite[n:]
 		}
 	}
+	return scanner.Err()
 }