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// +build static,system_libgit2
package main
import (
"bytes"
"context"
"encoding/gob"
"errors"
"flag"
"fmt"
"io"
"io/ioutil"
"os"
"os/exec"
"path/filepath"
git "github.com/libgit2/git2go/v31"
"gitlab.com/gitlab-org/gitaly/v14/internal/git2go"
)
type patchIterator struct {
value git2go.Patch
decoder *gob.Decoder
error error
}
func (iter *patchIterator) Next() bool {
if err := iter.decoder.Decode(&iter.value); err != nil {
if !errors.Is(err, io.EOF) {
iter.error = fmt.Errorf("decode patch: %w", err)
}
return false
}
return true
}
func (iter *patchIterator) Value() git2go.Patch { return iter.value }
func (iter *patchIterator) Err() error { return iter.error }
type applySubcommand struct {
gitBinaryPath string
}
func (cmd *applySubcommand) Flags() *flag.FlagSet {
fs := flag.NewFlagSet("apply", flag.ExitOnError)
fs.StringVar(&cmd.gitBinaryPath, "git-binary-path", "", "Path to the Git binary.")
return fs
}
// Run runs the subcommand.
func (cmd *applySubcommand) Run(ctx context.Context, stdin io.Reader, stdout io.Writer) error {
decoder := gob.NewDecoder(stdin)
var params git2go.ApplyParams
if err := decoder.Decode(¶ms); err != nil {
return fmt.Errorf("decode params: %w", err)
}
params.Patches = &patchIterator{decoder: decoder}
commitID, err := cmd.apply(ctx, params)
return gob.NewEncoder(stdout).Encode(git2go.Result{
CommitID: commitID,
Error: git2go.SerializableError(err),
})
}
func (cmd *applySubcommand) apply(ctx context.Context, params git2go.ApplyParams) (string, error) {
repo, err := git.OpenRepository(params.Repository)
if err != nil {
return "", fmt.Errorf("open repository: %w", err)
}
commitOID, err := git.NewOid(params.ParentCommit)
if err != nil {
return "", fmt.Errorf("parse parent commit oid: %w", err)
}
committer := git.Signature(params.Committer)
for i := 0; params.Patches.Next(); i++ {
commitOID, err = cmd.applyPatch(ctx, repo, &committer, commitOID, params.Patches.Value())
if err != nil {
return "", fmt.Errorf("apply patch [%d]: %w", i+1, err)
}
}
if err := params.Patches.Err(); err != nil {
return "", fmt.Errorf("reading patches: %w", err)
}
return commitOID.String(), nil
}
func (cmd *applySubcommand) applyPatch(
ctx context.Context,
repo *git.Repository,
committer *git.Signature,
parentCommitOID *git.Oid,
patch git2go.Patch,
) (*git.Oid, error) {
parentCommit, err := repo.LookupCommit(parentCommitOID)
if err != nil {
return nil, fmt.Errorf("lookup commit: %w", err)
}
parentTree, err := parentCommit.Tree()
if err != nil {
return nil, fmt.Errorf("lookup tree: %w", err)
}
diff, err := git.DiffFromBuffer(patch.Diff, repo)
if err != nil {
return nil, fmt.Errorf("diff from buffer: %w", err)
}
patchedIndex, err := repo.ApplyToTree(diff, parentTree, nil)
if err != nil {
if !git.IsErrorCode(err, git.ErrApplyFail) {
return nil, fmt.Errorf("apply to tree: %w", err)
}
patchedIndex, err = cmd.threeWayMerge(ctx, repo, parentTree, diff, patch.Diff)
if err != nil {
return nil, fmt.Errorf("three way merge: %w", err)
}
}
patchedTree, err := patchedIndex.WriteTreeTo(repo)
if err != nil {
return nil, fmt.Errorf("write patched tree: %w", err)
}
author := git.Signature(patch.Author)
patchedCommitOID, err := repo.CreateCommitFromIds("", &author, committer, patch.Message, patchedTree, parentCommitOID)
if err != nil {
return nil, fmt.Errorf("create commit: %w", err)
}
return patchedCommitOID, nil
}
// threeWayMerge attempts a three-way merge as a fallback if applying the patch fails.
// Fallback three-way merge is only possible if the patch records the pre-image blobs
// and the repository contains them. It works as follows:
//
// 1. An index that contains only the pre-image blobs of the patch is built. This is done
// by calling `git apply --build-fake-ancestor`. The tree of the index is the fake
// ancestor tree.
// 2. The fake ancestor tree is patched to produce the post-image tree of the patch.
// 3. Three-way merge is performed with fake ancestor tree as the common ancestor, the
// base commit's tree as our tree and the patched fake ancestor tree as their tree.
func (cmd *applySubcommand) threeWayMerge(
ctx context.Context,
repo *git.Repository,
our *git.Tree,
diff *git.Diff,
rawDiff []byte,
) (*git.Index, error) {
ancestorTree, err := cmd.buildFakeAncestor(ctx, repo, rawDiff)
if err != nil {
return nil, fmt.Errorf("build fake ancestor: %w", err)
}
patchedAncestorIndex, err := repo.ApplyToTree(diff, ancestorTree, nil)
if err != nil {
return nil, fmt.Errorf("patch fake ancestor: %w", err)
}
patchedAncestorTreeOID, err := patchedAncestorIndex.WriteTreeTo(repo)
if err != nil {
return nil, fmt.Errorf("write patched fake ancestor: %w", err)
}
patchedTree, err := repo.LookupTree(patchedAncestorTreeOID)
if err != nil {
return nil, fmt.Errorf("lookup patched tree: %w", err)
}
patchedIndex, err := repo.MergeTrees(ancestorTree, our, patchedTree, nil)
if err != nil {
return nil, fmt.Errorf("merge trees: %w", err)
}
if patchedIndex.HasConflicts() {
return nil, git2go.ErrMergeConflict
}
return patchedIndex, nil
}
func (cmd *applySubcommand) buildFakeAncestor(ctx context.Context, repo *git.Repository, diff []byte) (*git.Tree, error) {
dir, err := ioutil.TempDir("", "gitaly-git2go")
if err != nil {
return nil, fmt.Errorf("create temporary directory: %w", err)
}
defer os.RemoveAll(dir)
file := filepath.Join(dir, "patch-merge-index")
gitCmd := exec.CommandContext(ctx, cmd.gitBinaryPath, "--git-dir", repo.Path(), "apply", "--build-fake-ancestor", file)
gitCmd.Stdin = bytes.NewReader(diff)
if _, err := gitCmd.Output(); err != nil {
var exitError *exec.ExitError
if errors.As(err, &exitError) {
err = fmt.Errorf("%w, stderr: %q", err, exitError.Stderr)
}
return nil, fmt.Errorf("git: %w", err)
}
fakeAncestor, err := git.OpenIndex(file)
if err != nil {
return nil, fmt.Errorf("open fake ancestor index: %w", err)
}
ancestorTreeOID, err := fakeAncestor.WriteTreeTo(repo)
if err != nil {
return nil, fmt.Errorf("write fake ancestor tree: %w", err)
}
return repo.LookupTree(ancestorTreeOID)
}
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