Move catfile batch to a sub package of git module (#36232)

modules/git/catfile/batch.go

@@ -0,0 +1,178 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package catfile
+
+import (
+	"bufio"
+	"context"
+	"io"
+	"strings"
+
+	"code.gitea.io/gitea/modules/git/gitcmd"
+
+	"github.com/djherbis/buffer"
+	"github.com/djherbis/nio/v3"
+)
+
+// WriteCloserError wraps an io.WriteCloser with an additional CloseWithError function
+type WriteCloserError interface {
+	io.WriteCloser
+	CloseWithError(err error) error
+}
+
+type Batch interface {
+	Writer() WriteCloserError
+	Reader() *bufio.Reader
+	Close()
+}
+
+// batch represents an active `git cat-file --batch` or `--batch-check` invocation
+// paired with the pipes that feed/read from it. Call Close to release resources.
+type batch struct {
+	cancel context.CancelFunc
+	reader *bufio.Reader
+	writer WriteCloserError
+}
+
+// NewBatch creates a new cat-file --batch process for the provided repository path.
+// The returned Batch must be closed once the caller has finished with it.
+func NewBatch(ctx context.Context, repoPath string) (Batch, error) {
+	if err := EnsureValidGitRepository(ctx, repoPath); err != nil {
+		return nil, err
+	}
+
+	var batch batch
+	batch.writer, batch.reader, batch.cancel = catFileBatch(ctx, repoPath)
+	return &batch, nil
+}
+
+// NewBatchCheck creates a cat-file --batch-check process for the provided repository path.
+// The returned Batch must be closed once the caller has finished with it.
+func NewBatchCheck(ctx context.Context, repoPath string) (Batch, error) {
+	if err := EnsureValidGitRepository(ctx, repoPath); err != nil {
+		return nil, err
+	}
+
+	var check batch
+	check.writer, check.reader, check.cancel = catFileBatchCheck(ctx, repoPath)
+	return &check, nil
+}
+
+func (b *batch) Writer() WriteCloserError {
+	return b.writer
+}
+
+func (b *batch) Reader() *bufio.Reader {
+	return b.reader
+}
+
+// Close stops the underlying git cat-file process and releases held resources.
+func (b *batch) Close() {
+	if b == nil || b.cancel == nil {
+		return
+	}
+	b.cancel()
+	b.reader = nil
+	b.writer = nil
+	b.cancel = nil
+}
+
+// EnsureValidGitRepository runs `git rev-parse` in the repository path to make sure
+// the directory is a valid git repository. This avoids git cat-file hanging indefinitely
+// when invoked in invalid paths.
+func EnsureValidGitRepository(ctx context.Context, repoPath string) error {
+	stder := strings.Builder{}
+	err := gitcmd.NewCommand("rev-parse").
+		WithDir(repoPath).
+		WithStderr(&stder).
+		Run(ctx)
+	if err != nil {
+		return gitcmd.ConcatenateError(err, stder.String())
+	}
+	return nil
+}
+
+// catFileBatch opens git cat-file --batch in the provided repo and returns a stdin pipe,
+// a stdout reader and a cancel function.
+func catFileBatch(ctx context.Context, repoPath string) (WriteCloserError, *bufio.Reader, func()) {
+	batchStdinReader, batchStdinWriter := io.Pipe()
+	batchStdoutReader, batchStdoutWriter := nio.Pipe(buffer.New(32 * 1024))
+	ctx, ctxCancel := context.WithCancel(ctx)
+	closed := make(chan struct{})
+	cancel := func() {
+		ctxCancel()
+		_ = batchStdinWriter.Close()
+		_ = batchStdoutReader.Close()
+		<-closed
+	}
+
+	go func() {
+		<-ctx.Done()
+		cancel()
+	}()
+
+	go func() {
+		stder := strings.Builder{}
+		err := gitcmd.NewCommand("cat-file", "--batch").
+			WithDir(repoPath).
+			WithStdin(batchStdinReader).
+			WithStdout(batchStdoutWriter).
+			WithStderr(&stder).
+			WithUseContextTimeout(true).
+			Run(ctx)
+		if err != nil {
+			_ = batchStdoutWriter.CloseWithError(gitcmd.ConcatenateError(err, stder.String()))
+			_ = batchStdinReader.CloseWithError(gitcmd.ConcatenateError(err, stder.String()))
+		} else {
+			_ = batchStdoutWriter.Close()
+			_ = batchStdinReader.Close()
+		}
+		close(closed)
+	}()
+
+	batchReader := bufio.NewReaderSize(batchStdoutReader, 32*1024)
+	return batchStdinWriter, batchReader, cancel
+}
+
+// catFileBatchCheck opens git cat-file --batch-check in the provided repo and returns a stdin pipe,
+// a stdout reader and cancel function.
+func catFileBatchCheck(ctx context.Context, repoPath string) (WriteCloserError, *bufio.Reader, func()) {
+	batchStdinReader, batchStdinWriter := io.Pipe()
+	batchStdoutReader, batchStdoutWriter := io.Pipe()
+	ctx, ctxCancel := context.WithCancel(ctx)
+	closed := make(chan struct{})
+	cancel := func() {
+		ctxCancel()
+		_ = batchStdoutReader.Close()
+		_ = batchStdinWriter.Close()
+		<-closed
+	}
+
+	go func() {
+		<-ctx.Done()
+		cancel()
+	}()
+
+	go func() {
+		stder := strings.Builder{}
+		err := gitcmd.NewCommand("cat-file", "--batch-check").
+			WithDir(repoPath).
+			WithStdin(batchStdinReader).
+			WithStdout(batchStdoutWriter).
+			WithStderr(&stder).
+			WithUseContextTimeout(true).
+			Run(ctx)
+		if err != nil {
+			_ = batchStdoutWriter.CloseWithError(gitcmd.ConcatenateError(err, stder.String()))
+			_ = batchStdinReader.CloseWithError(gitcmd.ConcatenateError(err, stder.String()))
+		} else {
+			_ = batchStdoutWriter.Close()
+			_ = batchStdinReader.Close()
+		}
+		close(closed)
+	}()
+
+	batchReader := bufio.NewReader(batchStdoutReader)
+	return batchStdinWriter, batchReader, cancel
+}