restore: add --delete option to remove files that are not in snapshot

cmd/restic/cmd_restore.go

@@ -51,6 +51,7 @@ type RestoreOptions struct {
 	Sparse    bool
 	Verify    bool
 	Overwrite restorer.OverwriteBehavior
+	Delete    bool
 }
 
 var restoreOptions RestoreOptions
@@ -69,6 +70,7 @@ func init() {
 	flags.BoolVar(&restoreOptions.Sparse, "sparse", false, "restore files as sparse")
 	flags.BoolVar(&restoreOptions.Verify, "verify", false, "verify restored files content")
 	flags.Var(&restoreOptions.Overwrite, "overwrite", "overwrite behavior, one of (always|if-changed|if-newer|never) (default: always)")
+	flags.BoolVar(&restoreOptions.Delete, "delete", false, "delete files from target directory if they do not exist in snapshot. Use '--dry-run -vv' to check what would be deleted")
 }
 
 func runRestore(ctx context.Context, opts RestoreOptions, gopts GlobalOptions,
@@ -149,6 +151,7 @@ func runRestore(ctx context.Context, opts RestoreOptions, gopts GlobalOptions,
 		Sparse:    opts.Sparse,
 		Progress:  progress,
 		Overwrite: opts.Overwrite,
+		Delete:    opts.Delete,
 	})
 
 	totalErrors := 0

internal/restorer/restorer.go

@@ -25,8 +25,10 @@ type Restorer struct {
 
 	fileList map[string]bool
 
-	Error        func(location string, err error) error
-	Warn         func(message string)
+	Error func(location string, err error) error
+	Warn  func(message string)
+	// SelectFilter determines whether the item is selectedForRestore or whether a childMayBeSelected.
+	// selectedForRestore must not depend on isDir as `removeUnexpectedFiles` always passes false to isDir.
 	SelectFilter func(item string, dstpath string, isDir bool) (selectedForRestore bool, childMayBeSelected bool)
 }
 
@@ -444,6 +446,12 @@ func (res *Restorer) RestoreTo(ctx context.Context, dst string) error {
 			return nil
 		},
 		leaveDir: func(node *restic.Node, target, location string, expectedFilenames []string) error {
+			if res.opts.Delete {
+				if err := res.removeUnexpectedFiles(target, location, expectedFilenames); err != nil {
+					return err
+				}
+			}
+
 			if node == nil {
 				return nil
 			}
@@ -458,6 +466,50 @@ func (res *Restorer) RestoreTo(ctx context.Context, dst string) error {
 	return err
 }
 
+func (res *Restorer) removeUnexpectedFiles(target, location string, expectedFilenames []string) error {
+	if !res.opts.Delete {
+		panic("internal error")
+	}
+
+	entries, err := fs.Readdirnames(fs.Local{}, target, fs.O_NOFOLLOW)
+	if errors.Is(err, os.ErrNotExist) {
+		return nil
+	} else if err != nil {
+		return err
+	}
+
+	keep := map[string]struct{}{}
+	for _, name := range expectedFilenames {
+		keep[name] = struct{}{}
+	}
+
+	for _, entry := range entries {
+		if _, ok := keep[entry]; ok {
+			continue
+		}
+
+		nodeTarget := filepath.Join(target, entry)
+		nodeLocation := filepath.Join(location, entry)
+
+		if target == nodeTarget || !fs.HasPathPrefix(target, nodeTarget) {
+			return fmt.Errorf("skipping deletion due to invalid filename: %v", entry)
+		}
+
+		// TODO pass a proper value to the isDir parameter once this becomes relevant for the filters
+		selectedForRestore, _ := res.SelectFilter(nodeLocation, nodeTarget, false)
+		// only delete files that were selected for restore
+		if selectedForRestore {
+			if !res.opts.DryRun {
+				if err := fs.RemoveAll(nodeTarget); err != nil {
+					return err
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
 func (res *Restorer) trackFile(location string, metadataOnly bool) {
 	res.fileList[location] = metadataOnly
 }

internal/restorer/restorer_test.go

@@ -1219,3 +1219,115 @@ func TestRestoreDryRun(t *testing.T) {
 	_, err := os.Stat(tempdir)
 	rtest.Assert(t, errors.Is(err, os.ErrNotExist), "expected no file to be created, got %v", err)
 }
+
+func TestRestoreDelete(t *testing.T) {
+	repo := repository.TestRepository(t)
+	tempdir := rtest.TempDir(t)
+
+	sn, _ := saveSnapshot(t, repo, Snapshot{
+		Nodes: map[string]Node{
+			"dir": Dir{
+				Mode: normalizeFileMode(0755 | os.ModeDir),
+				Nodes: map[string]Node{
+					"file1":       File{Data: "content: file\n"},
+					"anotherfile": File{Data: "content: file\n"},
+				},
+			},
+			"dir2": Dir{
+				Mode: normalizeFileMode(0755 | os.ModeDir),
+				Nodes: map[string]Node{
+					"anotherfile": File{Data: "content: file\n"},
+				},
+			},
+			"anotherfile": File{Data: "content: file\n"},
+		},
+	}, noopGetGenericAttributes)
+
+	// should delete files that no longer exist in the snapshot
+	deleteSn, _ := saveSnapshot(t, repo, Snapshot{
+		Nodes: map[string]Node{
+			"dir": Dir{
+				Mode: normalizeFileMode(0755 | os.ModeDir),
+				Nodes: map[string]Node{
+					"file1": File{Data: "content: file\n"},
+				},
+			},
+		},
+	}, noopGetGenericAttributes)
+
+	tests := []struct {
+		selectFilter func(item string, dstpath string, isDir bool) (selectedForRestore bool, childMayBeSelected bool)
+		fileState    map[string]bool
+	}{
+		{
+			selectFilter: nil,
+			fileState: map[string]bool{
+				"dir":                                true,
+				filepath.Join("dir", "anotherfile"):  false,
+				filepath.Join("dir", "file1"):        true,
+				"dir2":                               false,
+				filepath.Join("dir2", "anotherfile"): false,
+				"anotherfile":                        false,
+			},
+		},
+		{
+			selectFilter: func(item, dstpath string, isDir bool) (selectedForRestore bool, childMayBeSelected bool) {
+				return false, false
+			},
+			fileState: map[string]bool{
+				"dir":                                true,
+				filepath.Join("dir", "anotherfile"):  true,
+				filepath.Join("dir", "file1"):        true,
+				"dir2":                               true,
+				filepath.Join("dir2", "anotherfile"): true,
+				"anotherfile":                        true,
+			},
+		},
+		{
+			selectFilter: func(item, dstpath string, isDir bool) (selectedForRestore bool, childMayBeSelected bool) {
+				switch item {
+				case filepath.FromSlash("/dir"):
+					selectedForRestore = true
+				case filepath.FromSlash("/dir2"):
+					selectedForRestore = true
+				}
+				return
+			},
+			fileState: map[string]bool{
+				"dir":                                true,
+				filepath.Join("dir", "anotherfile"):  true,
+				filepath.Join("dir", "file1"):        true,
+				"dir2":                               false,
+				filepath.Join("dir2", "anotherfile"): false,
+				"anotherfile":                        true,
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			res := NewRestorer(repo, sn, Options{})
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+
+			err := res.RestoreTo(ctx, tempdir)
+			rtest.OK(t, err)
+
+			res = NewRestorer(repo, deleteSn, Options{Delete: true})
+			if test.selectFilter != nil {
+				res.SelectFilter = test.selectFilter
+			}
+			err = res.RestoreTo(ctx, tempdir)
+			rtest.OK(t, err)
+
+			for fn, shouldExist := range test.fileState {
+				_, err := os.Stat(filepath.Join(tempdir, fn))
+				if shouldExist {
+					rtest.OK(t, err)
+				} else {
+					rtest.Assert(t, errors.Is(err, os.ErrNotExist), "file %v: unexpected error got %v, expected ErrNotExist", fn, err)
+				}
+			}
+		})
+	}
+}