Method GetDiffPreview

internal/database/repo_editor.go:246–301

GetDiffPreview produces and returns diff result of a file which is not yet committed.

(branch, treePath, content string)

// GetDiffPreview produces and returns diff result of a file which is not yet committed.
func (r *Repository) GetDiffPreview(branch, treePath, content string) (*gitutil.Diff, error) {
	// 🚨 SECURITY: Prevent uploading files into the ".git" directory.
	if isRepositoryGitPath(treePath) {
		return nil, errors.Errorf("bad tree path %q", treePath)
	}

	repoWorkingPool.CheckIn(com.ToStr(r.ID))
	defer repoWorkingPool.CheckOut(com.ToStr(r.ID))

	if err := r.DiscardLocalRepoBranchChanges(branch); err != nil {
		return nil, errors.Newf("discard local repo branch[%s] changes: %v", branch, err)
	} else if err = r.UpdateLocalCopyBranch(branch); err != nil {
		return nil, errors.Newf("update local copy branch[%s]: %v", branch, err)
	}

	localPath := r.LocalCopyPath()
	filePath := path.Join(localPath, treePath)

	// 🚨 SECURITY: Prevent touching files in surprising places, reject operations
	// that involve symlinks.
	if hasSymlinkInPath(localPath, treePath) {
		return nil, errors.New("cannot update file with symbolic link in path")
	}

	if err := os.MkdirAll(path.Dir(filePath), os.ModePerm); err != nil {
		return nil, errors.Wrap(err, "create parent directories")
	} else if err = os.WriteFile(filePath, []byte(content), 0o600); err != nil {
		return nil, errors.Newf("write file: %v", err)
	}

	// 🚨 SECURITY: Prevent including unintended options in the path to the Git command.
	cmd := exec.Command("git", "diff", "--end-of-options", treePath)
	cmd.Dir = localPath
	cmd.Stderr = os.Stderr

	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return nil, errors.Newf("get stdout pipe: %v", err)
	}

	if err = cmd.Start(); err != nil {
		return nil, errors.Newf("start: %v", err)
	}

	pid := process.Add(fmt.Sprintf("GetDiffPreview [repo_path: %s]", r.RepoPath()), cmd)
	defer process.Remove(pid)

	diff, err := gitutil.ParseDiff(stdout, conf.Git.MaxDiffFiles, conf.Git.MaxDiffLines, conf.Git.MaxDiffLineChars)
	if err != nil {
		return nil, errors.Newf("parse diff: %v", err)
	}
	if err = cmd.Wait(); err != nil {
		return nil, errors.Newf("wait: %v", err)
	}
	return diff, nil
}

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