// Copyright 2019 The Gitea Authors.// All rights reserved.// SPDX-License-Identifier: MIT package pull import (	"bytes"	"context"	"fmt"	"io"	"os"	"path/filepath"	"strings" 	"forgejo.org/models"	git_model "forgejo.org/models/git"	issues_model "forgejo.org/models/issues"	"forgejo.org/modules/git"	"forgejo.org/modules/gitrepo"	"forgejo.org/modules/graceful"	"forgejo.org/modules/log"	"forgejo.org/modules/process"	"forgejo.org/modules/util" 	"github.com/gobwas/glob") // DownloadDiffOrPatch will write the patch for the pr to the writerfunc DownloadDiffOrPatch(ctx context.Context, pr *issues_model.PullRequest, w io.Writer, patch, binary bool) error {	if err := pr.LoadBaseRepo(ctx); err != nil {		log.Error("Unable to load base repository ID %d for pr #%d [%d]", pr.BaseRepoID, pr.Index, pr.ID)		return err	} 	gitRepo, closer, err := gitrepo.RepositoryFromContextOrOpen(ctx, pr.BaseRepo)	if err != nil {		return fmt.Errorf("OpenRepository: %w", err)	}	defer closer.Close() 	if err := gitRepo.GetDiffOrPatch(pr.MergeBase, pr.GetGitRefName(), w, patch, binary); err != nil {		log.Error("Unable to get patch file from %s to %s in %s Error: %v", pr.MergeBase, pr.HeadBranch, pr.BaseRepo.FullName(), err)		return fmt.Errorf("Unable to get patch file from %s to %s in %s Error: %w", pr.MergeBase, pr.HeadBranch, pr.BaseRepo.FullName(), err)	}	return nil} // TestPatch will test whether a simple patch will applyfunc TestPatch(pr *issues_model.PullRequest) error {	ctx, _, finished := process.GetManager().AddContext(graceful.GetManager().HammerContext(), fmt.Sprintf("TestPatch: %s", pr))	defer finished() 	testPatchCtx, err := testPatch(ctx, pr)	testPatchCtx.close()	return err} type testPatchContext struct {	headRev        string	headIsCommitID bool	baseRev        string	env            []string	gitRepo        *git.Repository	close          func()} // LoadHeadRevision loads the necessary information to access the head revision.func (t *testPatchContext) LoadHeadRevision(ctx context.Context, pr *issues_model.PullRequest) error {	// If AGit, then use HeadCommitID if set (AGit flow creates pull request),	// otherwise use the pull request reference.	if pr.Flow == issues_model.PullRequestFlowAGit {		if len(pr.HeadCommitID) > 0 {			t.headRev = pr.HeadCommitID			t.headIsCommitID = true			return nil		}		t.headRev = pr.GetGitRefName()		return nil	} 	// If it is within the same repository, simply return the branch name.	if pr.BaseRepoID == pr.HeadRepoID {		t.headRev = pr.GetGitHeadBranchRefName()		return nil	} 	// We are in Github flow, head and base repository are different.	// Resolve the head branch to a commitID and return a Git alternate	// environment for the head repository.	gitRepo, err := git.OpenRepository(ctx, pr.HeadRepo.RepoPath())	if err != nil {		return err	}	defer gitRepo.Close() 	headCommitID, err := gitRepo.GetRefCommitID(pr.GetGitHeadBranchRefName())	if err != nil {		return err	} 	t.headRev = headCommitID	t.headIsCommitID = true	t.env = append(os.Environ(), `GIT_ALTERNATE_OBJECT_DIRECTORIES=`+pr.HeadRepo.RepoPath()+"/objects")	return nil} // getTestPatchCtx constructs a new testpatch context for the given pull request.// If `onBare` is true, then the context will use the base repository that does// not contain a working tree. Otherwise a temprorary repository is created that// contains a working tree.func getTestPatchCtx(ctx context.Context, pr *issues_model.PullRequest, onBare bool) (*testPatchContext, error) {	testPatchCtx := &testPatchContext{		close: func() {},	} 	if onBare {		if err := pr.LoadBaseRepo(ctx); err != nil {			return testPatchCtx, fmt.Errorf("LoadBaseRepo: %w", err)		}		if err := pr.LoadHeadRepo(ctx); err != nil {			return testPatchCtx, fmt.Errorf("LoadHeadRepo: %w", err)		} 		if err := testPatchCtx.LoadHeadRevision(ctx, pr); err != nil {			return testPatchCtx, fmt.Errorf("LoadHeadRevision: %w", err)		} 		gitRepo, err := git.OpenRepository(ctx, pr.BaseRepo.RepoPath())		if err != nil {			return testPatchCtx, fmt.Errorf("OpenRepository: %w", err)		} 		testPatchCtx.baseRev = git.BranchPrefix + pr.BaseBranch		testPatchCtx.gitRepo = gitRepo		testPatchCtx.close = func() {			gitRepo.Close()		}	} else {		prCtx, cancel, err := createTemporaryRepoForPR(ctx, pr)		if err != nil {			return testPatchCtx, fmt.Errorf("createTemporaryRepoForPR: %w", err)		}		testPatchCtx.close = cancel 		gitRepo, err := git.OpenRepository(ctx, prCtx.tmpBasePath)		if err != nil {			return testPatchCtx, fmt.Errorf("OpenRepository: %w", err)		} 		testPatchCtx.baseRev = git.BranchPrefix + baseBranch		testPatchCtx.headRev = git.BranchPrefix + trackingBranch		testPatchCtx.gitRepo = gitRepo		testPatchCtx.close = func() {			cancel()			gitRepo.Close()		}	}	return testPatchCtx, nil} func testPatch(ctx context.Context, pr *issues_model.PullRequest) (*testPatchContext, error) {	testPatchCtx, err := getTestPatchCtx(ctx, pr, git.SupportGitMergeTree)	if err != nil {		return testPatchCtx, fmt.Errorf("getTestPatchCtx: %w", err)	} 	// 1. update merge base	pr.MergeBase, _, err = git.NewCommand(ctx, "merge-base").AddDashesAndList(testPatchCtx.baseRev, testPatchCtx.headRev).RunStdString(&git.RunOpts{Dir: testPatchCtx.gitRepo.Path, Env: testPatchCtx.env})	if err != nil {		var err2 error		pr.MergeBase, err2 = testPatchCtx.gitRepo.GetRefCommitID(testPatchCtx.baseRev)		if err2 != nil {			return testPatchCtx, fmt.Errorf("GetMergeBase: %v and can't find commit ID for base: %w", err, err2)		}	}	pr.MergeBase = strings.TrimSpace(pr.MergeBase) 	if testPatchCtx.headIsCommitID {		pr.HeadCommitID = testPatchCtx.headRev	} else {		if pr.HeadCommitID, err = testPatchCtx.gitRepo.GetRefCommitID(testPatchCtx.headRev); err != nil {			return testPatchCtx, fmt.Errorf("GetRefCommitID: can't find commit ID for head: %w", err)		}	} 	// If the head commit is equal to the merge base it roughly means that the	// head commit is a parent of the base commit.	if pr.HeadCommitID == pr.MergeBase {		pr.Status = issues_model.PullRequestStatusAncestor		return testPatchCtx, nil	} 	// 2. Check for conflicts	if conflicts, err := checkConflicts(ctx, pr, testPatchCtx); err != nil || conflicts || pr.Status == issues_model.PullRequestStatusEmpty {		if err != nil {			return testPatchCtx, fmt.Errorf("checkConflicts: %w", err)		}		return testPatchCtx, nil	} 	// 3. Check for protected files changes	if err = checkPullFilesProtection(ctx, pr, testPatchCtx); err != nil {		return testPatchCtx, fmt.Errorf("checkPullFilesProtection: %v", err)	} 	if len(pr.ChangedProtectedFiles) > 0 {		log.Trace("Found %d protected files changed", len(pr.ChangedProtectedFiles))	} 	pr.Status = issues_model.PullRequestStatusMergeable 	return testPatchCtx, nil} type errMergeConflict struct {	filename string} func (e *errMergeConflict) Error() string {	return fmt.Sprintf("conflict detected at: %s", e.filename)} func attemptMerge(ctx context.Context, file *unmergedFile, tmpBasePath string, filesToRemove *[]string, filesToAdd *[]git.IndexObjectInfo) error {	log.Trace("Attempt to merge:\n%v", file) 	switch {	case file.stage1 != nil && (file.stage2 == nil || file.stage3 == nil):		// 1. Deleted in one or both:		//		// Conflict <==> the stage1 !SameAs to the undeleted one		if (file.stage2 != nil && !file.stage1.SameAs(file.stage2)) || (file.stage3 != nil && !file.stage1.SameAs(file.stage3)) {			// Conflict!			return &errMergeConflict{file.stage1.path}		} 		// Not a genuine conflict and we can simply remove the file from the index		*filesToRemove = append(*filesToRemove, file.stage1.path)		return nil	case file.stage1 == nil && file.stage2 != nil && (file.stage3 == nil || file.stage2.SameAs(file.stage3)):		// 2. Added in ours but not in theirs or identical in both		//		// Not a genuine conflict just add to the index		*filesToAdd = append(*filesToAdd, git.IndexObjectInfo{Mode: file.stage2.mode, Object: git.MustIDFromString(file.stage2.sha), Filename: file.stage2.path})		return nil	case file.stage1 == nil && file.stage2 != nil && file.stage3 != nil && file.stage2.sha == file.stage3.sha && file.stage2.mode != file.stage3.mode:		// 3. Added in both with the same sha but the modes are different		//		// Conflict! (Not sure that this can actually happen but we should handle)		return &errMergeConflict{file.stage2.path}	case file.stage1 == nil && file.stage2 == nil && file.stage3 != nil:		// 4. Added in theirs but not ours:		//		// Not a genuine conflict just add to the index		*filesToAdd = append(*filesToAdd, git.IndexObjectInfo{Mode: file.stage3.mode, Object: git.MustIDFromString(file.stage3.sha), Filename: file.stage3.path})		return nil	case file.stage1 == nil:		// 5. Created by new in both		//		// Conflict!		return &errMergeConflict{file.stage2.path}	case file.stage2 != nil && file.stage3 != nil:		// 5. Modified in both - we should try to merge in the changes but first:		//		if file.stage2.mode == "120000" || file.stage3.mode == "120000" {			// 5a. Conflicting symbolic link change			return &errMergeConflict{file.stage2.path}		}		if file.stage2.mode == "160000" || file.stage3.mode == "160000" {			// 5b. Conflicting submodule change			return &errMergeConflict{file.stage2.path}		}		if file.stage2.mode != file.stage3.mode {			// 5c. Conflicting mode change			return &errMergeConflict{file.stage2.path}		} 		// Need to get the objects from the object db to attempt to merge		root, _, err := git.NewCommand(ctx, "unpack-file").AddDynamicArguments(file.stage1.sha).RunStdString(&git.RunOpts{Dir: tmpBasePath})		if err != nil {			return fmt.Errorf("unable to get root object: %s at path: %s for merging. Error: %w", file.stage1.sha, file.stage1.path, err)		}		root = strings.TrimSpace(root)		defer func() {			_ = util.Remove(filepath.Join(tmpBasePath, root))		}() 		base, _, err := git.NewCommand(ctx, "unpack-file").AddDynamicArguments(file.stage2.sha).RunStdString(&git.RunOpts{Dir: tmpBasePath})		if err != nil {			return fmt.Errorf("unable to get base object: %s at path: %s for merging. Error: %w", file.stage2.sha, file.stage2.path, err)		}		base = strings.TrimSpace(filepath.Join(tmpBasePath, base))		defer func() {			_ = util.Remove(base)		}()		head, _, err := git.NewCommand(ctx, "unpack-file").AddDynamicArguments(file.stage3.sha).RunStdString(&git.RunOpts{Dir: tmpBasePath})		if err != nil {			return fmt.Errorf("unable to get head object:%s at path: %s for merging. Error: %w", file.stage3.sha, file.stage3.path, err)		}		head = strings.TrimSpace(head)		defer func() {			_ = util.Remove(filepath.Join(tmpBasePath, head))		}() 		// now git merge-file annoyingly takes a different order to the merge-tree ...		_, _, conflictErr := git.NewCommand(ctx, "merge-file").AddDynamicArguments(base, root, head).RunStdString(&git.RunOpts{Dir: tmpBasePath})		if conflictErr != nil {			return &errMergeConflict{file.stage2.path}		} 		// base now contains the merged data		hash, _, err := git.NewCommand(ctx, "hash-object", "-w", "--path").AddDynamicArguments(file.stage2.path, base).RunStdString(&git.RunOpts{Dir: tmpBasePath})		if err != nil {			return err		}		hash = strings.TrimSpace(hash)		*filesToAdd = append(*filesToAdd, git.IndexObjectInfo{Mode: file.stage2.mode, Object: git.MustIDFromString(hash), Filename: file.stage2.path})		return nil	default:		if file.stage1 != nil {			return &errMergeConflict{file.stage1.path}		} else if file.stage2 != nil {			return &errMergeConflict{file.stage2.path}		} else if file.stage3 != nil {			return &errMergeConflict{file.stage3.path}		}	}	return nil} // AttemptThreeWayMerge will attempt to three way merge using git read-tree and then follow the git merge-one-file algorithm to attempt to resolve basic conflictsfunc AttemptThreeWayMerge(ctx context.Context, gitRepo *git.Repository, base, ours, theirs, description string) (bool, []string, error) {	ctx, cancel := context.WithCancel(ctx)	defer cancel() 	// First we use read-tree to do a simple three-way merge	if _, _, err := git.NewCommand(ctx, "read-tree", "-m").AddDynamicArguments(base, ours, theirs).RunStdString(&git.RunOpts{Dir: gitRepo.Path}); err != nil {		log.Error("Unable to run read-tree -m! Error: %v", err)		return false, nil, fmt.Errorf("unable to run read-tree -m! Error: %w", err)	} 	var filesToRemove []string	var filesToAdd []git.IndexObjectInfo 	// Then we use git ls-files -u to list the unmerged files and collate the triples in unmergedfiles	unmerged := make(chan *unmergedFile)	go unmergedFiles(ctx, gitRepo.Path, unmerged) 	defer func() {		cancel()		for range unmerged {			// empty the unmerged channel		}	}() 	numberOfConflicts := 0	conflict := false	conflictedFiles := make([]string, 0, 5) 	for file := range unmerged {		if file == nil {			break		}		if file.err != nil {			cancel()			return false, nil, file.err		} 		// OK now we have the unmerged file triplet attempt to merge it		if err := attemptMerge(ctx, file, gitRepo.Path, &filesToRemove, &filesToAdd); err != nil {			if conflictErr, ok := err.(*errMergeConflict); ok {				log.Trace("Conflict: %s in %s", conflictErr.filename, description)				conflict = true				if numberOfConflicts < 10 {					conflictedFiles = append(conflictedFiles, conflictErr.filename)				}				numberOfConflicts++				continue			}			return false, nil, err		}	} 	// Add and remove files in one command, as this is slow with many files otherwise	if err := gitRepo.RemoveFilesFromIndex(filesToRemove...); err != nil {		return false, nil, err	}	if err := gitRepo.AddObjectsToIndex(filesToAdd...); err != nil {		return false, nil, err	} 	return conflict, conflictedFiles, nil} // MergeTree runs a 3-way merge between `ours` and `theirs` with// `base` as the merge base.//// It uses git-merge-tree(1) to do this merge without requiring a work-tree and// can run in a base repository. It returns the object ID of the merge tree, if// there are any conflicts and conflicted files.func MergeTree(ctx context.Context, gitRepo *git.Repository, base, ours, theirs string, env []string) (string, bool, []string, error) {	cmd := git.NewCommand(ctx, "merge-tree", "--write-tree", "-z", "--name-only", "--no-messages")	if git.CheckGitVersionAtLeast("2.40") == nil {		cmd.AddOptionFormat("--merge-base=%s", base)	} 	stdout := &bytes.Buffer{}	gitErr := cmd.AddDynamicArguments(ours, theirs).Run(&git.RunOpts{Dir: gitRepo.Path, Stdout: stdout, Env: env})	if gitErr != nil && !git.IsErrorExitCode(gitErr, 1) {		log.Error("Unable to run merge-tree: %v", gitErr)		return "", false, nil, fmt.Errorf("unable to run merge-tree: %w", gitErr)	} 	// There are two situations that we consider for the output:	// 1. Clean merge and the output is <OID of toplevel tree>NUL	// 2. Merge conflict and the output is <OID of toplevel tree>NUL<Conflicted file info>NUL	treeOID, conflictedFileInfo, _ := strings.Cut(stdout.String(), "\x00")	if len(conflictedFileInfo) == 0 {		return treeOID, git.IsErrorExitCode(gitErr, 1), nil, nil	} 	// Remove last NULL-byte from conflicted file info, then split with NULL byte as seperator.	return treeOID, true, strings.Split(conflictedFileInfo[:len(conflictedFileInfo)-1], "\x00"), nil} // checkConflicts takes a pull request and checks if merging it would result in// merge conflicts and checks if the diff is empty; the status is set accordingly.func checkConflicts(ctx context.Context, pr *issues_model.PullRequest, testPatchCtx *testPatchContext) (bool, error) {	// Resets the conflict status.	pr.ConflictedFiles = nil 	if git.SupportGitMergeTree {		// Check for conflicts via a merge-tree.		treeHash, conflict, conflictFiles, err := MergeTree(ctx, testPatchCtx.gitRepo, pr.MergeBase, testPatchCtx.baseRev, testPatchCtx.headRev, testPatchCtx.env)		if err != nil {			return false, fmt.Errorf("MergeTree: %w", err)		} 		if !conflict {			// No conflicts were detected, now check if the pull request actually			// contains anything useful via a diff. git-diff-tree(1) with --quiet			// will return exit code 0 if there's no diff and exit code 1 if there's			// a diff.			err := git.NewCommand(ctx, "diff-tree", "--quiet").AddDynamicArguments(treeHash, pr.MergeBase).Run(&git.RunOpts{Dir: testPatchCtx.gitRepo.Path, Env: testPatchCtx.env})			isEmpty := true			if err != nil {				if git.IsErrorExitCode(err, 1) {					isEmpty = false				} else {					return false, fmt.Errorf("DiffTree: %w", err)				}			} 			if isEmpty {				log.Debug("PullRequest[%d]: Patch is empty - ignoring", pr.ID)				pr.Status = issues_model.PullRequestStatusEmpty			}			return false, nil		} 		pr.Status = issues_model.PullRequestStatusConflict		pr.ConflictedFiles = conflictFiles 		log.Trace("Found %d files conflicted: %v", len(pr.ConflictedFiles), pr.ConflictedFiles)		return true, nil	} 	// 2. AttemptThreeWayMerge first - this is much quicker than plain patch to base	description := fmt.Sprintf("PR[%d] %s/%s#%d", pr.ID, pr.BaseRepo.OwnerName, pr.BaseRepo.Name, pr.Index)	conflict, conflictFiles, err := AttemptThreeWayMerge(ctx, testPatchCtx.gitRepo, pr.MergeBase, testPatchCtx.baseRev, testPatchCtx.headRev, description)	if err != nil {		return false, err	} 	if !conflict {		// No conflicts detected so we need to check if the patch is empty...		// a. Write the newly merged tree and check the new tree-hash		var treeHash string		treeHash, _, err = git.NewCommand(ctx, "write-tree").RunStdString(&git.RunOpts{Dir: testPatchCtx.gitRepo.Path})		if err != nil {			lsfiles, _, _ := git.NewCommand(ctx, "ls-files", "-u").RunStdString(&git.RunOpts{Dir: testPatchCtx.gitRepo.Path})			return false, fmt.Errorf("unable to write unconflicted tree: %w\n`git ls-files -u`:\n%s", err, lsfiles)		}		treeHash = strings.TrimSpace(treeHash)		baseTree, err := testPatchCtx.gitRepo.GetTree(testPatchCtx.baseRev)		if err != nil {			return false, err		} 		// b. compare the new tree-hash with the base tree hash		if treeHash == baseTree.ID.String() {			log.Debug("PullRequest[%d]: Patch is empty - ignoring", pr.ID)			pr.Status = issues_model.PullRequestStatusEmpty		} 		return false, nil	} 	pr.Status = issues_model.PullRequestStatusConflict	pr.ConflictedFiles = conflictFiles

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