Fix #732: Add LFS objects to base repository on merging (#7082)

On merge we walk the merge history and ensure that all lfs objects pointed to in
the history are added to the base repository. This switches from relying on having git-lfs installed on the server, (and in fact .gitattributes being correctly installed.)

modules/pull/lfs.go

@@ -0,0 +1,226 @@
+// Copyright 2019 The Gitea Authors.
+// All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package pull
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"sync"
+
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/lfs"
+	"code.gitea.io/gitea/modules/log"
+)
+
+// LFSPush pushes lfs objects referred to in new commits in the head repository from the base repository
+func LFSPush(tmpBasePath, mergeHeadSHA, mergeBaseSHA string, pr *models.PullRequest) error {
+	// Now we have to implement git lfs push
+	// git rev-list --objects --filter=blob:limit=1k HEAD --not base
+	// pass blob shas in to git cat-file --batch-check (possibly unnecessary)
+	// ensure only blobs and <=1k size then pass in to git cat-file --batch
+	// to read each sha and check each as a pointer
+	// Then if they are lfs -> add them to the baseRepo
+	revListReader, revListWriter := io.Pipe()
+	shasToCheckReader, shasToCheckWriter := io.Pipe()
+	catFileCheckReader, catFileCheckWriter := io.Pipe()
+	shasToBatchReader, shasToBatchWriter := io.Pipe()
+	catFileBatchReader, catFileBatchWriter := io.Pipe()
+	errChan := make(chan error, 1)
+	wg := sync.WaitGroup{}
+	wg.Add(6)
+	// Create the go-routines in reverse order.
+
+	// 6. Take the output of cat-file --batch and check if each file in turn
+	// to see if they're pointers to files in the LFS store associated with
+	// the head repo and add them to the base repo if so
+	go readCatFileBatch(catFileBatchReader, &wg, pr)
+
+	// 5. Take the shas of the blobs and batch read them
+	go doCatFileBatch(shasToBatchReader, catFileBatchWriter, &wg, tmpBasePath)
+
+	// 4. From the provided objects restrict to blobs <=1k
+	go readCatFileBatchCheck(catFileCheckReader, shasToBatchWriter, &wg)
+
+	// 3. Run batch-check on the objects retrieved from rev-list
+	go doCatFileBatchCheck(shasToCheckReader, catFileCheckWriter, &wg, tmpBasePath)
+
+	// 2. Check each object retrieved rejecting those without names as they will be commits or trees
+	go readRevListObjects(revListReader, shasToCheckWriter, &wg)
+
+	// 1. Run rev-list objects from mergeHead to mergeBase
+	go doRevListObjects(revListWriter, &wg, tmpBasePath, mergeHeadSHA, mergeBaseSHA, errChan)
+
+	wg.Wait()
+	select {
+	case err, has := <-errChan:
+		if has {
+			return err
+		}
+	default:
+	}
+	return nil
+}
+
+func doRevListObjects(revListWriter *io.PipeWriter, wg *sync.WaitGroup, tmpBasePath, headSHA, baseSHA string, errChan chan<- error) {
+	defer wg.Done()
+	defer revListWriter.Close()
+	stderr := new(bytes.Buffer)
+	var errbuf strings.Builder
+	cmd := git.NewCommand("rev-list", "--objects", headSHA, "--not", baseSHA)
+	if err := cmd.RunInDirPipeline(tmpBasePath, revListWriter, stderr); err != nil {
+		log.Error("git rev-list [%s]: %v - %s", tmpBasePath, err, errbuf.String())
+		errChan <- fmt.Errorf("git rev-list [%s]: %v - %s", tmpBasePath, err, errbuf.String())
+	}
+}
+
+func readRevListObjects(revListReader *io.PipeReader, shasToCheckWriter *io.PipeWriter, wg *sync.WaitGroup) {
+	defer wg.Done()
+	defer revListReader.Close()
+	defer shasToCheckWriter.Close()
+	scanner := bufio.NewScanner(revListReader)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if len(line) == 0 {
+			continue
+		}
+		fields := strings.Split(line, " ")
+		if len(fields) < 2 || len(fields[1]) == 0 {
+			continue
+		}
+		toWrite := []byte(fields[0] + "\n")
+		for len(toWrite) > 0 {
+			n, err := shasToCheckWriter.Write(toWrite)
+			if err != nil {
+				_ = revListReader.CloseWithError(err)
+				break
+			}
+			toWrite = toWrite[n:]
+		}
+	}
+	_ = shasToCheckWriter.CloseWithError(scanner.Err())
+}
+
+func doCatFileBatchCheck(shasToCheckReader *io.PipeReader, catFileCheckWriter *io.PipeWriter, wg *sync.WaitGroup, tmpBasePath string) {
+	defer wg.Done()
+	defer shasToCheckReader.Close()
+	defer catFileCheckWriter.Close()
+
+	stderr := new(bytes.Buffer)
+	var errbuf strings.Builder
+	cmd := git.NewCommand("cat-file", "--batch-check")
+	if err := cmd.RunInDirFullPipeline(tmpBasePath, catFileCheckWriter, stderr, shasToCheckReader); err != nil {
+		_ = catFileCheckWriter.CloseWithError(fmt.Errorf("git cat-file --batch-check [%s]: %v - %s", tmpBasePath, err, errbuf.String()))
+	}
+}
+
+func readCatFileBatchCheck(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())
+	}()
+	for scanner.Scan() {
+		line := scanner.Text()
+		if len(line) == 0 {
+			continue
+		}
+		fields := strings.Split(line, " ")
+		if len(fields) < 3 || fields[1] != "blob" {
+			continue
+		}
+		size, _ := strconv.Atoi(string(fields[2]))
+		if size > 1024 {
+			continue
+		}
+		toWrite := []byte(fields[0] + "\n")
+		for len(toWrite) > 0 {
+			n, err := shasToBatchWriter.Write(toWrite)
+			if err != nil {
+				_ = catFileCheckReader.CloseWithError(err)
+				break
+			}
+			toWrite = toWrite[n:]
+		}
+	}
+}
+
+func doCatFileBatch(shasToBatchReader *io.PipeReader, catFileBatchWriter *io.PipeWriter, wg *sync.WaitGroup, tmpBasePath string) {
+	defer wg.Done()
+	defer shasToBatchReader.Close()
+	defer catFileBatchWriter.Close()
+
+	stderr := new(bytes.Buffer)
+	var errbuf strings.Builder
+	if err := git.NewCommand("cat-file", "--batch").RunInDirFullPipeline(tmpBasePath, catFileBatchWriter, stderr, shasToBatchReader); err != nil {
+		_ = shasToBatchReader.CloseWithError(fmt.Errorf("git rev-list [%s]: %v - %s", tmpBasePath, err, errbuf.String()))
+	}
+}
+
+func readCatFileBatch(catFileBatchReader *io.PipeReader, wg *sync.WaitGroup, pr *models.PullRequest) {
+	defer wg.Done()
+	defer catFileBatchReader.Close()
+
+	bufferedReader := bufio.NewReader(catFileBatchReader)
+	buf := make([]byte, 1025)
+	for {
+		// File descriptor line: sha
+		_, err := bufferedReader.ReadString(' ')
+		if err != nil {
+			_ = catFileBatchReader.CloseWithError(err)
+			break
+		}
+		// Throw away the blob
+		if _, err := bufferedReader.ReadString(' '); err != nil {
+			_ = catFileBatchReader.CloseWithError(err)
+			break
+		}
+		sizeStr, err := bufferedReader.ReadString('\n')
+		if err != nil {
+			_ = catFileBatchReader.CloseWithError(err)
+			break
+		}
+		size, err := strconv.Atoi(sizeStr[:len(sizeStr)-1])
+		if err != nil {
+			_ = catFileBatchReader.CloseWithError(err)
+			break
+		}
+		pointerBuf := buf[:size+1]
+		if _, err := io.ReadFull(bufferedReader, pointerBuf); err != nil {
+			_ = catFileBatchReader.CloseWithError(err)
+			break
+		}
+		pointerBuf = pointerBuf[:size]
+		// Now we need to check if the pointerBuf is an LFS pointer
+		pointer := lfs.IsPointerFile(&pointerBuf)
+		if pointer == nil {
+			continue
+		}
+		// Then we need to check that this pointer is in the db
+		if _, err := pr.HeadRepo.GetLFSMetaObjectByOid(pointer.Oid); err != nil {
+			if err == models.ErrLFSObjectNotExist {
+				log.Warn("During merge of: %d in %-v, there is a pointer to LFS Oid: %s which although present in the LFS store is not associated with the head repo %-v", pr.Index, pr.BaseRepo, pointer.Oid, pr.HeadRepo)
+				continue
+			}
+			_ = catFileBatchReader.CloseWithError(err)
+			break
+		}
+		// OK we have a pointer that is associated with the head repo
+		// and is actually a file in the LFS
+		// Therefore it should be associated with the base repo
+		pointer.RepositoryID = pr.BaseRepoID
+		if _, err := models.NewLFSMetaObject(pointer); err != nil {
+			_ = catFileBatchReader.CloseWithError(err)
+			break
+		}
+	}
+}