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/lfs_nogogit.go

@@ -12,34 +12,27 @@ import (
 	"io"
 	"sort"
 	"strings"
-	"sync"
 
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/git/gitcmd"
 )
 
 // FindLFSFile finds commits that contain a provided pointer file hash
-func FindLFSFile(repo *git.Repository, objectID git.ObjectID) ([]*LFSResult, error) {
+func FindLFSFile(repo *git.Repository, objectID git.ObjectID) (results []*LFSResult, _ error) {
+	cmd := gitcmd.NewCommand("rev-list", "--all")
+	revListReader, revListReaderClose := cmd.MakeStdoutPipe()
+	defer revListReaderClose()
+	err := cmd.WithDir(repo.Path).
+		WithPipelineFunc(func(context gitcmd.Context) (err error) {
+			results, err = findLFSFileFunc(repo, objectID, revListReader)
+			return err
+		}).RunWithStderr(repo.Ctx)
+	return results, err
+}
+
+func findLFSFileFunc(repo *git.Repository, objectID git.ObjectID, revListReader io.Reader) ([]*LFSResult, error) {
 	resultsMap := map[string]*LFSResult{}
 	results := make([]*LFSResult, 0)
-
-	basePath := repo.Path
-
-	// Use rev-list to provide us with all commits in order
-	revListReader, revListWriter := io.Pipe()
-	defer func() {
-		_ = revListWriter.Close()
-		_ = revListReader.Close()
-	}()
-
-	go func() {
-		err := gitcmd.NewCommand("rev-list", "--all").
-			WithDir(repo.Path).
-			WithStdout(revListWriter).
-			RunWithStderr(repo.Ctx)
-		_ = revListWriter.CloseWithError(err)
-	}()
-
 	// Next feed the commits in order into cat-file --batch, followed by their trees and sub trees as necessary.
 	// so let's create a batch stdin and stdout
 	batch, cancel, err := repo.CatFileBatch(repo.Ctx)
@@ -158,56 +151,6 @@ func FindLFSFile(repo *git.Repository, objectID git.ObjectID) ([]*LFSResult, err
 	}
 
 	sort.Sort(lfsResultSlice(results))
-
-	// Should really use a go-git function here but name-rev is not completed and recapitulating it is not simple
-	shasToNameReader, shasToNameWriter := io.Pipe()
-	nameRevStdinReader, nameRevStdinWriter := io.Pipe()
-	errChan := make(chan error, 1)
-	wg := sync.WaitGroup{}
-	wg.Add(3)
-
-	go func() {
-		defer wg.Done()
-		scanner := bufio.NewScanner(nameRevStdinReader)
-		i := 0
-		for scanner.Scan() {
-			line := scanner.Text()
-			if len(line) == 0 {
-				continue
-			}
-			result := results[i]
-			result.FullCommitName = line
-			result.BranchName = strings.Split(line, "~")[0]
-			i++
-		}
-	}()
-	go NameRevStdin(repo.Ctx, shasToNameReader, nameRevStdinWriter, &wg, basePath)
-	go func() {
-		defer wg.Done()
-		defer shasToNameWriter.Close()
-		for _, result := range results {
-			_, err := shasToNameWriter.Write([]byte(result.SHA))
-			if err != nil {
-				errChan <- err
-				break
-			}
-			_, err = shasToNameWriter.Write([]byte{'\n'})
-			if err != nil {
-				errChan <- err
-				break
-			}
-		}
-	}()
-
-	wg.Wait()
-
-	select {
-	case err, has := <-errChan:
-		if has {
-			return nil, lfsError("unable to obtain name for LFS files", err)
-		}
-	default:
-	}
-
-	return results, nil
+	err = fillResultNameRev(repo.Ctx, repo.Path, results)
+	return results, err
 }