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applier.go
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applier.go
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// Package patch2pr converts Git patches in to GitHub pull requests.
package patch2pr
import (
"bytes"
"context"
"encoding/base64"
"errors"
"fmt"
"io/ioutil"
"strconv"
"strings"
"time"
"github.com/bluekeyes/go-gitdiff/gitdiff"
"github.com/google/go-github/v63/github"
)
// DefaultCommitMessage is the commit message used when no message is provided
// in a patch header.
var DefaultCommitMessage = "Apply patch with patch2pr"
// Applier applies patches to create trees and commits in a repository.
type Applier struct {
client *github.Client
owner string
repo string
commit *github.Commit
tree string
treeCache map[string]*github.Tree
entries map[string]*github.TreeEntry
uncommitted bool
}
// NewApplier creates a new Applier for a repository. The Applier applies
// changes on top of commit c.
func NewApplier(client *github.Client, repo Repository, c *github.Commit) *Applier {
a := &Applier{
client: client,
owner: repo.Owner,
repo: repo.Name,
}
a.Reset(c)
return a
}
// Apply applies the changes in a file, adds the result to the list of pending
// tree entries, and returns the entry. If the application succeeds, Apply
// creates a blob in the repository with the modified content.
func (a *Applier) Apply(ctx context.Context, f *gitdiff.File) (*github.TreeEntry, error) {
// TODO(bkeyes): validate file to make sure fields are consistent
// maybe two modes: validate and fix, where fix tries to set
// missing fields based on the framents or the set fields
//
// in particular, we need IsNew, IsDelete, maybe IsCopy and IsRename to
// agree with the fragments and NewName/OldName
var entry *github.TreeEntry
var err error
switch {
case f.IsNew:
entry, err = a.applyCreate(ctx, f)
case f.IsDelete:
entry, err = a.applyDelete(ctx, f)
default:
entry, err = a.applyModify(ctx, f)
}
if err != nil {
return nil, err
}
if entry.Content != nil {
blob, _, err := a.client.Git.CreateBlob(ctx, a.owner, a.repo, &github.Blob{
Content: entry.Content,
Encoding: github.String("base64"),
})
if err != nil {
return nil, fmt.Errorf("create blob failed: %w", err)
}
entry.SHA = blob.SHA
entry.Content = nil
}
return entry, nil
}
func (a *Applier) applyCreate(ctx context.Context, f *gitdiff.File) (*github.TreeEntry, error) {
_, exists, err := a.getEntry(ctx, f.NewName)
if err != nil {
return nil, err
}
if exists {
return nil, errors.New("existing entry for new file")
}
c, err := base64Apply(nil, f)
if err != nil {
return nil, err
}
path := f.NewName
newEntry := &github.TreeEntry{
Path: &path,
Mode: github.String(getMode(f, nil)),
Type: github.String("blob"),
Content: &c,
}
a.entries[path] = newEntry
return newEntry, nil
}
func (a *Applier) applyDelete(ctx context.Context, f *gitdiff.File) (*github.TreeEntry, error) {
entry, exists, err := a.getEntry(ctx, f.OldName)
if err != nil {
return nil, err
}
if !exists {
// because the rest of application is strict, return an error if the
// file was already deleted, since it indicates a conflict of some kind
return nil, errors.New("missing entry for deleted file")
}
data, _, err := a.client.Git.GetBlobRaw(ctx, a.owner, a.repo, entry.GetSHA())
if err != nil {
return nil, fmt.Errorf("get blob content failed: %w", err)
}
if err := gitdiff.Apply(ioutil.Discard, bytes.NewReader(data), f); err != nil {
return nil, err
}
path := f.OldName
newEntry := &github.TreeEntry{
Path: &path,
Mode: entry.Mode,
}
a.entries[path] = newEntry
return newEntry, nil
}
func (a *Applier) applyModify(ctx context.Context, f *gitdiff.File) (*github.TreeEntry, error) {
entry, exists, err := a.getEntry(ctx, f.OldName)
if err != nil {
return nil, err
}
if !exists {
return nil, errors.New("no entry for modified file")
}
path := f.NewName
newEntry := &github.TreeEntry{
Path: &path,
Mode: github.String(getMode(f, entry)),
Type: github.String("blob"),
}
if len(f.TextFragments) > 0 || f.BinaryFragment != nil {
data, _, err := a.client.Git.GetBlobRaw(ctx, a.owner, a.repo, entry.GetSHA())
if err != nil {
return nil, fmt.Errorf("get blob content failed: %w", err)
}
c, err := base64Apply(data, f)
if err != nil {
return nil, err
}
newEntry.Content = &c
}
// delete the old file if it was renamed
if f.OldName != f.NewName {
path := f.OldName
a.entries[path] = &github.TreeEntry{
Path: &path,
Mode: entry.Mode,
}
}
if newEntry.Content == nil {
newEntry.SHA = entry.SHA
}
a.entries[path] = newEntry
return newEntry, nil
}
// Entries returns the list of pending tree entries.
func (a *Applier) Entries() []*github.TreeEntry {
entries := make([]*github.TreeEntry, 0, len(a.entries))
for _, e := range a.entries {
entries = append(entries, e)
}
return entries
}
// CreateTree creates a tree from the pending tree entries and clears the entry
// list. The new tree serves as the base tree for future Apply calls.
// CreateTree returns an error if there are no pending tree entires.
func (a *Applier) CreateTree(ctx context.Context) (*github.Tree, error) {
if len(a.entries) == 0 {
return nil, errors.New("no pending tree entries")
}
tree, _, err := a.client.Git.CreateTree(ctx, a.owner, a.repo, a.tree, a.Entries())
if err != nil {
return nil, err
}
// Clear the tree cache here because we only cache trees that lead to file
// modifications, and any change creates a new (i.e. uncached) tree SHA
a.tree = tree.GetSHA()
a.treeCache = make(map[string]*github.Tree)
a.entries = make(map[string]*github.TreeEntry)
a.uncommitted = true
return tree, nil
}
// Commit commits the latest tree, optionally using the details in tmpl and
// header. If there are pending tree entries, it calls CreateTree before
// creating the commit. It returns an error if there are no pending trees or
// tree entries.
//
// If tmpl is not nil, Commit uses it as a template for the new commit,
// overwriting fields as needed. If header is not nil, Commit uses it to set
// the message, author, and committer for the new commit. Values in header
// overwrite those in tmpl.
//
// If both tmpl and header are nil or missing fields, Commit uses a default
// message, the current time, and the authenticated user as needed for the
// commit details.
func (a *Applier) Commit(ctx context.Context, tmpl *github.Commit, header *gitdiff.PatchHeader) (*github.Commit, error) {
if !a.uncommitted && len(a.entries) == 0 {
return nil, errors.New("no pending tree or tree entries")
}
if len(a.entries) > 0 {
if _, err := a.CreateTree(ctx); err != nil {
return nil, fmt.Errorf("create tree failed: %w", err)
}
}
var c github.Commit
if tmpl != nil {
c = *tmpl
}
c.Tree = &github.Tree{
SHA: github.String(a.tree),
}
c.Parents = []*github.Commit{
a.commit,
}
if header != nil {
c.Message = github.String(header.Message())
c.Author = makeCommitAuthor(header.Author, header.AuthorDate)
c.Committer = makeCommitAuthor(header.Committer, header.CommitterDate)
}
if c.Message == nil || *c.Message == "" {
c.Message = github.String("Apply patch with patch2pr")
}
commit, _, err := a.client.Git.CreateCommit(ctx, a.owner, a.repo, &c, nil)
if err != nil {
return nil, err
}
a.commit = commit
a.uncommitted = false
return commit, nil
}
// Reset resets the applier so that future Apply calls start from commit c. It
// removes pending tree entries and clears the latest tree. Reset does not
// modify the remote repository.
func (a *Applier) Reset(c *github.Commit) {
a.commit = c
a.tree = c.GetTree().GetSHA()
a.treeCache = make(map[string]*github.Tree)
a.entries = make(map[string]*github.TreeEntry)
a.uncommitted = false
}
// getEntry returns the tree entry for a path. If the path has a pending
// change, return the entry representing that change, otherwise return an entry
// from the base tree. Returns nil and false if no entry exists for path.
func (a *Applier) getEntry(ctx context.Context, path string) (*github.TreeEntry, bool, error) {
if entry, ok := a.entries[path]; ok {
if entry.SHA == nil && entry.Content == nil {
// The existing entry is a deletion, so pretend it doesn't exist
return nil, false, nil
}
return entry, true, nil
}
parts := strings.Split(path, "/")
dir, name := parts[:len(parts)-1], parts[len(parts)-1]
tree, err := a.getTree(ctx, a.tree)
if err != nil {
return nil, false, err
}
for _, s := range dir {
entry, ok := findTreeEntry(tree, s, "tree")
if !ok {
return nil, false, nil
}
tree, err = a.getTree(ctx, entry.GetSHA())
if err != nil {
return nil, false, err
}
}
entry, ok := findTreeEntry(tree, name, "blob")
return entry, ok, nil
}
func (a *Applier) getTree(ctx context.Context, sha string) (*github.Tree, error) {
if tree, ok := a.treeCache[sha]; ok {
return tree, nil
}
tree, _, err := a.client.Git.GetTree(ctx, a.owner, a.repo, sha, false)
if err != nil {
return nil, fmt.Errorf("get tree %s failed: %w", sha, err)
}
a.treeCache[sha] = tree
return tree, nil
}
func findTreeEntry(t *github.Tree, name, entryType string) (*github.TreeEntry, bool) {
for _, entry := range t.Entries {
if entry.GetPath() == name && entry.GetType() == entryType {
return entry, true
}
}
return nil, false
}
func base64Apply(data []byte, f *gitdiff.File) (string, error) {
var b bytes.Buffer
enc := base64.NewEncoder(base64.StdEncoding, &b)
if err := gitdiff.Apply(enc, bytes.NewReader(data), f); err != nil {
return "", err
}
if err := enc.Close(); err != nil {
return "", fmt.Errorf("base64 encoding failed: %w", err)
}
return b.String(), nil
}
// TODO(bkeyes): extract this to go-gitdiff in some form?
func getMode(f *gitdiff.File, existing *github.TreeEntry) string {
switch {
case f.NewMode > 0:
return strconv.FormatInt(int64(f.NewMode), 8)
case existing != nil && existing.GetMode() != "":
return existing.GetMode()
case f.OldMode > 0:
return strconv.FormatInt(int64(f.OldMode), 8)
}
return "100644"
}
func makeCommitAuthor(id *gitdiff.PatchIdentity, d time.Time) *github.CommitAuthor {
if id == nil && d.IsZero() {
return nil
}
a := &github.CommitAuthor{}
if id != nil {
if id.Name != "" {
a.Name = github.String(id.Name)
}
if id.Email != "" {
a.Email = github.String(id.Email)
}
}
if !d.IsZero() {
a.Date = &github.Timestamp{Time: d}
}
return a
}