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/repo_ref_nogogit.go

@@ -15,69 +15,61 @@ import (
 
 // GetRefsFiltered returns all references of the repository that matches patterm exactly or starting with.
 func (repo *Repository) GetRefsFiltered(pattern string) ([]*Reference, error) {
-	stdoutReader, stdoutWriter := io.Pipe()
-	defer func() {
-		_ = stdoutReader.Close()
-		_ = stdoutWriter.Close()
-	}()
-
-	go func() {
-		err := gitcmd.NewCommand("for-each-ref").
-			WithDir(repo.Path).
-			WithStdout(stdoutWriter).
-			Run(repo.Ctx)
-		_ = stdoutWriter.CloseWithError(err)
-	}()
-
 	refs := make([]*Reference, 0)
-	bufReader := bufio.NewReader(stdoutReader)
-	for {
-		// The output of for-each-ref is simply a list:
-		// <sha> SP <type> TAB <ref> LF
-		sha, err := bufReader.ReadString(' ')
-		if err == io.EOF {
-			break
-		}
-		if err != nil {
-			return nil, err
-		}
-		sha = sha[:len(sha)-1]
+	cmd := gitcmd.NewCommand("for-each-ref")
+	stdoutReader, stdoutReaderClose := cmd.MakeStdoutPipe()
+	defer stdoutReaderClose()
+	err := cmd.WithDir(repo.Path).
+		WithPipelineFunc(func(context gitcmd.Context) error {
+			bufReader := bufio.NewReader(stdoutReader)
+			for {
+				// The output of for-each-ref is simply a list:
+				// <sha> SP <type> TAB <ref> LF
+				sha, err := bufReader.ReadString(' ')
+				if err == io.EOF {
+					break
+				}
+				if err != nil {
+					return err
+				}
+				sha = sha[:len(sha)-1]
 
-		typ, err := bufReader.ReadString('\t')
-		if err == io.EOF {
-			// This should not happen, but we'll tolerate it
-			break
-		}
-		if err != nil {
-			return nil, err
-		}
-		typ = typ[:len(typ)-1]
+				typ, err := bufReader.ReadString('\t')
+				if err == io.EOF {
+					// This should not happen, but we'll tolerate it
+					break
+				}
+				if err != nil {
+					return err
+				}
+				typ = typ[:len(typ)-1]
 
-		refName, err := bufReader.ReadString('\n')
-		if err == io.EOF {
-			// This should not happen, but we'll tolerate it
-			break
-		}
-		if err != nil {
-			return nil, err
-		}
-		refName = refName[:len(refName)-1]
+				refName, err := bufReader.ReadString('\n')
+				if err == io.EOF {
+					// This should not happen, but we'll tolerate it
+					break
+				}
+				if err != nil {
+					return err
+				}
+				refName = refName[:len(refName)-1]
 
-		// refName cannot be HEAD but can be remotes or stash
-		if strings.HasPrefix(refName, RemotePrefix) || refName == "/refs/stash" {
-			continue
-		}
+				// refName cannot be HEAD but can be remotes or stash
+				if strings.HasPrefix(refName, RemotePrefix) || refName == "/refs/stash" {
+					continue
+				}
 
-		if pattern == "" || strings.HasPrefix(refName, pattern) {
-			r := &Reference{
-				Name:   refName,
-				Object: MustIDFromString(sha),
-				Type:   typ,
-				repo:   repo,
+				if pattern == "" || strings.HasPrefix(refName, pattern) {
+					r := &Reference{
+						Name:   refName,
+						Object: MustIDFromString(sha),
+						Type:   typ,
+						repo:   repo,
+					}
+					refs = append(refs, r)
+				}
 			}
-			refs = append(refs, r)
-		}
-	}
-
-	return refs, nil
+			return nil
+		}).RunWithStderr(repo.Ctx)
+	return refs, err
 }