Add --ignore-inode option to backup cmd

revised version of https://github.com/restic/restic/pull/2047

cmd/restic/cmd_backup.go

@@ -85,6 +85,7 @@ type BackupOptions struct {
 	FilesFrom           []string
 	TimeStamp           string
 	WithAtime           bool
+	IgnoreInode         bool
 }
 
 var backupOptions BackupOptions
@@ -112,6 +113,7 @@ func init() {
 	f.StringArrayVar(&backupOptions.FilesFrom, "files-from", nil, "read the files to backup from file (can be combined with file args/can be specified multiple times)")
 	f.StringVar(&backupOptions.TimeStamp, "time", "", "time of the backup (ex. '2012-11-01 22:08:41') (default: now)")
 	f.BoolVar(&backupOptions.WithAtime, "with-atime", false, "store the atime for all files and directories")
+	f.BoolVar(&backupOptions.IgnoreInode, "ignore-inode", false, "ignore inode number changes when checking for modified files")
 }
 
 // filterExisting returns a slice of all existing items, or an error if no
@@ -549,6 +551,7 @@ func runBackup(opts BackupOptions, gopts GlobalOptions, term *termstatus.Termina
 	arch.CompleteItem = p.CompleteItem
 	arch.StartFile = p.StartFile
 	arch.CompleteBlob = p.CompleteBlob
+	arch.IgnoreInode = opts.IgnoreInode
 
 	if parentSnapshotID == nil {
 		parentSnapshotID = &restic.ID{}

doc/040_backup.rst

@@ -279,6 +279,10 @@ written, and the next backup needs to write new metadata again. If you really
 want to save the access time for files and directories, you can pass the
 ``--with-atime`` option to the ``backup`` command.
 
+In filesystems that do not support inode consistency, like FUSE-based ones and pCloud, it is
+possible to ignore inode on changed files comparison by passing ``--ignore-inode`` to
+``backup`` command.
+
 Reading data from stdin
 ***********************
 

internal/archiver/archiver.go

@@ -79,6 +79,7 @@ type Archiver struct {
 	// be saved. Enabling it may result in much metadata, so it's off by
 	// default.
 	WithAtime bool
+	IgnoreInode bool
 }
 
 // Options is used to configure the archiver.
@@ -133,6 +134,7 @@ func New(repo restic.Repository, fs fs.FS, opts Options) *Archiver {
 		CompleteItem: func(string, *restic.Node, *restic.Node, ItemStats, time.Duration) {},
 		StartFile:    func(string) {},
 		CompleteBlob: func(string, uint64) {},
+		IgnoreInode:  false,
 	}
 
 	return arch
@@ -383,7 +385,7 @@ func (arch *Archiver) Save(ctx context.Context, snPath, target string, previous
 		}
 
 		// use previous node if the file hasn't changed
-		if previous != nil && !fileChanged(fi, previous) {
+		if previous != nil && !fileChanged(fi, previous, arch.IgnoreInode) {
 			debug.Log("%v hasn't changed, returning old node", target)
 			arch.CompleteItem(snPath, previous, previous, ItemStats{}, time.Since(start))
 			arch.CompleteBlob(snPath, previous.Size)
@@ -436,7 +438,7 @@ func (arch *Archiver) Save(ctx context.Context, snPath, target string, previous
 
 // fileChanged returns true if the file's content has changed since the node
 // was created.
-func fileChanged(fi os.FileInfo, node *restic.Node) bool {
+func fileChanged(fi os.FileInfo, node *restic.Node, ignoreInode bool) bool {
 	if node == nil {
 		return true
 	}
@@ -458,7 +460,7 @@ func fileChanged(fi os.FileInfo, node *restic.Node) bool {
 	}
 
 	// check inode
-	if node.Inode != extFI.Inode {
+	if !ignoreInode && node.Inode != extFI.Inode {
 		return true
 	}
 

internal/archiver/archiver_test.go

@@ -555,9 +555,11 @@ func TestFileChanged(t *testing.T) {
 	}
 
 	var tests = []struct {
-		Name    string
+		Name        string
-		Content []byte
+		Content     []byte
-		Modify  func(t testing.TB, filename string)
+		Modify      func(t testing.TB, filename string)
+		IgnoreInode bool
+		Check       bool
 	}{
 		{
 			Name: "same-content-new-file",
@@ -596,6 +598,18 @@ func TestFileChanged(t *testing.T) {
 				save(t, filename, defaultContent)
 			},
 		},
+		{
+			Name: "ignore-inode",
+			Modify: func(t testing.TB, filename string) {
+				fi := lstat(t, filename)
+				remove(t, filename)
+				sleep()
+				save(t, filename, defaultContent)
+				setTimestamp(t, filename, fi.ModTime(), fi.ModTime())
+			},
+			IgnoreInode: true,
+			Check: true,
+		},
 	}
 
 	for _, test := range tests {
@@ -613,15 +627,19 @@ func TestFileChanged(t *testing.T) {
 			fiBefore := lstat(t, filename)
 			node := nodeFromFI(t, filename, fiBefore)
 
-			if fileChanged(fiBefore, node) {
+			if fileChanged(fiBefore, node, false) {
 				t.Fatalf("unchanged file detected as changed")
 			}
 
 			test.Modify(t, filename)
 
 			fiAfter := lstat(t, filename)
-			if !fileChanged(fiAfter, node) {
+			if test.Check == fileChanged(fiAfter, node, test.IgnoreInode) {
-				t.Fatalf("modified file detected as unchanged")
+				if test.Check {
+					t.Fatalf("unmodified file detected as changed")
+				} else {
+					t.Fatalf("modified file detected as unchanged")
+				}
 			}
 		})
 	}
@@ -637,7 +655,7 @@ func TestFilChangedSpecialCases(t *testing.T) {
 
 	t.Run("nil-node", func(t *testing.T) {
 		fi := lstat(t, filename)
-		if !fileChanged(fi, nil) {
+		if !fileChanged(fi, nil, false) {
 			t.Fatal("nil node detected as unchanged")
 		}
 	})
@@ -646,7 +664,7 @@ func TestFilChangedSpecialCases(t *testing.T) {
 		fi := lstat(t, filename)
 		node := nodeFromFI(t, filename, fi)
 		node.Type = "symlink"
-		if !fileChanged(fi, node) {
+		if !fileChanged(fi, node, false) {
 			t.Fatal("node with changed type detected as unchanged")
 		}
 	})