// renameFile attempts to rename an existing file to a destination
// and set the right attributes on it.
func (f *rwFolder) renameFile(source, target protocol.FileInfo) {
	// Used in the defer closure below, updated by the function body. Take
	// care not declare another err.
	var err error

	events.Default.Log(events.ItemStarted, map[string]string{
		"folder": f.folderID,
		"item":   source.Name,
		"type":   "file",
		"action": "delete",
	})
	events.Default.Log(events.ItemStarted, map[string]string{
		"folder": f.folderID,
		"item":   target.Name,
		"type":   "file",
		"action": "update",
	})

	defer func() {
		events.Default.Log(events.ItemFinished, map[string]interface{}{
			"folder": f.folderID,
			"item":   source.Name,
			"error":  events.Error(err),
			"type":   "file",
			"action": "delete",
		})
		events.Default.Log(events.ItemFinished, map[string]interface{}{
			"folder": f.folderID,
			"item":   target.Name,
			"error":  events.Error(err),
			"type":   "file",
			"action": "update",
		})
	}()

	l.Debugln(f, "taking rename shortcut", source.Name, "->", target.Name)

	from, err := rootedJoinedPath(f.dir, source.Name)
	if err != nil {
		f.newError(source.Name, err)
		return
	}
	to, err := rootedJoinedPath(f.dir, target.Name)
	if err != nil {
		f.newError(target.Name, err)
		return
	}

	if f.versioner != nil {
		err = osutil.Copy(from, to)
		if err == nil {
			err = osutil.InWritableDir(f.versioner.Archive, from)
		}
	} else {
		err = osutil.TryRename(from, to)
	}

	if err == nil {
		// The file was renamed, so we have handled both the necessary delete
		// of the source and the creation of the target. Fix-up the metadata,
		// and update the local index of the target file.

		f.dbUpdates <- dbUpdateJob{source, dbUpdateDeleteFile}

		err = f.shortcutFile(target)
		if err != nil {
			l.Infof("Puller (folder %q, file %q): rename from %q metadata: %v", f.folderID, target.Name, source.Name, err)
			f.newError(target.Name, err)
			return
		}

		f.dbUpdates <- dbUpdateJob{target, dbUpdateHandleFile}
	} else {
		// We failed the rename so we have a source file that we still need to
		// get rid of. Attempt to delete it instead so that we make *some*
		// progress. The target is unhandled.

		err = osutil.InWritableDir(os.Remove, from)
		if err != nil {
			l.Infof("Puller (folder %q, file %q): delete %q after failed rename: %v", f.folderID, target.Name, source.Name, err)
			f.newError(target.Name, err)
			return
		}

		f.dbUpdates <- dbUpdateJob{source, dbUpdateDeleteFile}
	}
}

// renameFile attempts to rename an existing file to a destination
// and set the right attributes on it.
func (p *rwFolder) renameFile(source, target protocol.FileInfo) {
	var err error
	events.Default.Log(events.ItemStarted, map[string]string{
		"folder": p.folder,
		"item":   source.Name,
		"type":   "file",
		"action": "delete",
	})
	events.Default.Log(events.ItemStarted, map[string]string{
		"folder": p.folder,
		"item":   target.Name,
		"type":   "file",
		"action": "update",
	})
	defer func() {
		events.Default.Log(events.ItemFinished, map[string]interface{}{
			"folder": p.folder,
			"item":   source.Name,
			"error":  events.Error(err),
			"type":   "file",
			"action": "delete",
		})
		events.Default.Log(events.ItemFinished, map[string]interface{}{
			"folder": p.folder,
			"item":   target.Name,
			"error":  events.Error(err),
			"type":   "file",
			"action": "update",
		})
	}()

	if debug {
		l.Debugln(p, "taking rename shortcut", source.Name, "->", target.Name)
	}

	from := filepath.Join(p.dir, source.Name)
	to := filepath.Join(p.dir, target.Name)

	if p.versioner != nil {
		err = osutil.Copy(from, to)
		if err == nil {
			err = osutil.InWritableDir(p.versioner.Archive, from)
		}
	} else {
		err = osutil.TryRename(from, to)
	}

	if err == nil {
		// The file was renamed, so we have handled both the necessary delete
		// of the source and the creation of the target. Fix-up the metadata,
		// and update the local index of the target file.

		p.dbUpdates <- dbUpdateJob{source, dbUpdateDeleteFile}

		err = p.shortcutFile(target)
		if err != nil {
			l.Infof("Puller (folder %q, file %q): rename from %q metadata: %v", p.folder, target.Name, source.Name, err)
			p.newError(target.Name, err)
			return
		}

		p.dbUpdates <- dbUpdateJob{target, dbUpdateHandleFile}
	} else {
		// We failed the rename so we have a source file that we still need to
		// get rid of. Attempt to delete it instead so that we make *some*
		// progress. The target is unhandled.

		err = osutil.InWritableDir(osutil.Remove, from)
		if err != nil {
			l.Infof("Puller (folder %q, file %q): delete %q after failed rename: %v", p.folder, target.Name, source.Name, err)
			p.newError(target.Name, err)
			return
		}

		p.dbUpdates <- dbUpdateJob{source, dbUpdateDeleteFile}
	}
}

func (f *rwFolder) performFinish(state *sharedPullerState) error {
	// Set the correct permission bits on the new file
	if !f.ignorePermissions(state.file) {
		if err := os.Chmod(state.tempName, os.FileMode(state.file.Permissions&0777)); err != nil {
			return err
		}
	}

	if stat, err := f.mtimeFS.Lstat(state.realName); err == nil {
		// There is an old file or directory already in place. We need to
		// handle that.

		switch {
		case stat.IsDir() || stat.Mode()&os.ModeSymlink != 0:
			// It's a directory or a symlink. These are not versioned or
			// archived for conflicts, only removed (which of course fails for
			// non-empty directories).

			// TODO: This is the place where we want to remove temporary files
			// and future hard ignores before attempting a directory delete.
			// Should share code with f.deletDir().

			if err = osutil.InWritableDir(os.Remove, state.realName); err != nil {
				return err
			}

		case f.inConflict(state.version, state.file.Version):
			// The new file has been changed in conflict with the existing one. We
			// should file it away as a conflict instead of just removing or
			// archiving. Also merge with the version vector we had, to indicate
			// we have resolved the conflict.

			state.file.Version = state.file.Version.Merge(state.version)
			if err = osutil.InWritableDir(f.moveForConflict, state.realName); err != nil {
				return err
			}

		case f.versioner != nil:
			// If we should use versioning, let the versioner archive the old
			// file before we replace it. Archiving a non-existent file is not
			// an error.

			if err = f.versioner.Archive(state.realName); err != nil {
				return err
			}
		}
	}

	// Replace the original content with the new one. If it didn't work,
	// leave the temp file in place for reuse.
	if err := osutil.TryRename(state.tempName, state.realName); err != nil {
		return err
	}

	// Set the correct timestamp on the new file
	f.mtimeFS.Chtimes(state.realName, state.file.ModTime(), state.file.ModTime()) // never fails

	// Record the updated file in the index
	f.dbUpdates <- dbUpdateJob{state.file, dbUpdateHandleFile}
	return nil
}

func alterFiles(dir string) error {
	err := filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
		if os.IsNotExist(err) {
			// Something we deleted. Never mind.
			return nil
		}

		info, err = os.Stat(path)
		if err != nil {
			// Something we deleted while walking. Ignore.
			return nil
		}

		if strings.HasPrefix(filepath.Base(path), "test-") {
			return nil
		}

		switch filepath.Base(path) {
		case ".stfolder":
			return nil
		case ".stversions":
			return nil
		}

		// File structure is base/x/xy/xyz12345...
		// comps == 1: base (don't touch)
		// comps == 2: base/x (must be dir)
		// comps == 3: base/x/xy (must be dir)
		// comps  > 3: base/x/xy/xyz12345... (can be dir or file)

		comps := len(strings.Split(path, string(os.PathSeparator)))

		r := rand.Intn(10)
		switch {
		case r == 0 && comps > 2:
			// Delete every tenth file or directory, except top levels
			return removeAll(path)

		case r == 1 && info.Mode().IsRegular():
			if info.Mode()&0200 != 0200 {
				// Not owner writable. Fix.
				if err = os.Chmod(path, 0644); err != nil {
					return err
				}
			}

			// Overwrite a random kilobyte of every tenth file
			fd, err := os.OpenFile(path, os.O_RDWR, 0644)
			if err != nil {
				return err
			}
			if info.Size() > 1024 {
				_, err = fd.Seek(rand.Int63n(info.Size()), os.SEEK_SET)
				if err != nil {
					return err
				}
			}
			_, err = io.Copy(fd, io.LimitReader(cr.Reader, 1024))
			if err != nil {
				return err
			}
			return fd.Close()

		// Change capitalization
		case r == 2 && comps > 3 && rand.Float64() < 0.2:
			if runtime.GOOS == "darwin" || runtime.GOOS == "windows" {
				// Syncthing is currently broken for case-only renames on case-
				// insensitive platforms.
				// https://github.com/syncthing/syncthing/issues/1787
				return nil
			}

			base := []rune(filepath.Base(path))
			for i, r := range base {
				if rand.Float64() < 0.5 {
					base[i] = unicode.ToLower(r)
				} else {
					base[i] = unicode.ToUpper(r)
				}
			}
			newPath := filepath.Join(filepath.Dir(path), string(base))
			if newPath != path {
				return osutil.TryRename(path, newPath)
			}

		// Switch between files and directories
		case r == 3 && comps > 3 && rand.Float64() < 0.2:
			if !info.Mode().IsRegular() {
				err = removeAll(path)
				if err != nil {
					return err
				}
				d1 := []byte("I used to be a dir: " + path)
				err := ioutil.WriteFile(path, d1, 0644)
				if err != nil {
					return err
				}
			} else {
				err := osutil.Remove(path)
				if err != nil {
//.........这里部分代码省略.........