sync: add --track-renames-strategy leaf

See: https://forum.rclone.org/t/how-to-minimize-bandwith-w-r-t-renames-during-sync/16928/22

docs/content/docs.md

@@ -1324,13 +1324,25 @@ Note also that `--track-renames` is incompatible with
 `--delete-before` and will select `--delete-after` instead of
 `--delete-during`.
 
-### --track-renames-strategy (hash,modtime) ###
+### --track-renames-strategy (hash,modtime,leaf,size) ###
 
-This option changes the matching criteria for `--track-renames` to match
-by any combination of modtime, hash, size. Matching by size is always enabled
-no matter what option is selected here. This also means
-that it enables `--track-renames` support for encrypted destinations.
-If nothing is specified, the default option is matching by hashes.
+This option changes the matching criteria for `--track-renames`.
+
+The matching is controlled by a comma separated selection of these tokens:
+
+- `modtime` - the modification time of the file - not supported on all backends
+- `hash` - the hash of the file contents - not supported on all backends
+- `leaf` - the name of the file not including its directory name
+- `size` - the size of the file (this is always enabled)
+
+So using `--track-renames-strategy modtime,leaf` would match files
+based on modification time, the leaf of the file name and the size
+only.
+
+Using `--track-renames-strategy modtime` or `leaf` can enable
+`--track-renames` support for encrypted destinations.
+
+If nothing is specified, the default option is matching by `hash`es.
 
 ### --delete-(before,during,after) ###
 

fs/config/configflags/configflags.go

@@ -65,7 +65,7 @@ func AddFlags(flagSet *pflag.FlagSet) {
 	flags.BoolVarP(flagSet, &deleteAfter, "delete-after", "", false, "When synchronizing, delete files on destination after transferring (default)")
 	flags.Int64VarP(flagSet, &fs.Config.MaxDelete, "max-delete", "", -1, "When synchronizing, limit the number of deletes")
 	flags.BoolVarP(flagSet, &fs.Config.TrackRenames, "track-renames", "", fs.Config.TrackRenames, "When synchronizing, track file renames and do a server side move if possible")
-	flags.StringVarP(flagSet, &fs.Config.TrackRenamesStrategy, "track-renames-strategy", "", fs.Config.TrackRenamesStrategy, "Strategies to use when synchronizing using track-renames hash|modtime")
+	flags.StringVarP(flagSet, &fs.Config.TrackRenamesStrategy, "track-renames-strategy", "", fs.Config.TrackRenamesStrategy, "Strategies to use when synchronizing using track-renames hash|modtime|leaf")
 	flags.IntVarP(flagSet, &fs.Config.LowLevelRetries, "low-level-retries", "", fs.Config.LowLevelRetries, "Number of low level retries to do.")
 	flags.BoolVarP(flagSet, &fs.Config.UpdateOlder, "update", "u", fs.Config.UpdateOlder, "Skip files that are newer on the destination.")
 	flags.BoolVarP(flagSet, &fs.Config.UseServerModTime, "use-server-modtime", "", fs.Config.UseServerModTime, "Use server modified time instead of object metadata")

fs/sync/sync.go

@@ -76,6 +76,7 @@ type trackRenamesStrategy byte
 const (
 	trackRenamesStrategyHash trackRenamesStrategy = 1 << iota
 	trackRenamesStrategyModtime
+	trackRenamesStrategyLeaf
 )
 
 func (strategy trackRenamesStrategy) hash() bool {
@@ -86,6 +87,10 @@ func (strategy trackRenamesStrategy) modTime() bool {
 	return (strategy & trackRenamesStrategyModtime) != 0
 }
 
+func (strategy trackRenamesStrategy) leaf() bool {
+	return (strategy & trackRenamesStrategyLeaf) != 0
+}
+
 func newSyncCopyMove(ctx context.Context, fdst, fsrc fs.Fs, deleteMode fs.DeleteMode, DoMove bool, deleteEmptySrcDirs bool, copyEmptySrcDirs bool) (*syncCopyMove, error) {
 	if (deleteMode != fs.DeleteModeOff || DoMove) && operations.Overlapping(fdst, fsrc) {
 		return nil, fserrors.FatalError(fs.ErrorOverlapping)
@@ -609,6 +614,8 @@ func parseTrackRenamesStrategy(strategies string) (strategy trackRenamesStrategy
 			strategy |= trackRenamesStrategyHash
 		case "modtime":
 			strategy |= trackRenamesStrategyModtime
+		case "leaf":
+			strategy |= trackRenamesStrategyLeaf
 		case "size":
 			// ignore
 		default:
@@ -638,12 +645,18 @@ func (s *syncCopyMove) renameID(obj fs.Object, renamesStrategy trackRenamesStrat
 			return ""
 		}
 
-		fmt.Fprintf(&builder, ",%s", hash)
+		builder.WriteRune(',')
+		builder.WriteString(hash)
 	}
 
 	// for renamesStrategy.modTime() we don't add to the hash but we check the times in
 	// popRenameMap
 
+	if renamesStrategy.leaf() {
+		builder.WriteRune(',')
+		builder.WriteString(path.Base(obj.Remote()))
+	}
+
 	return builder.String()
 }
 

fs/sync/sync_test.go

@@ -1162,6 +1162,44 @@ func TestSyncWithTrackRenamesStrategyModtime(t *testing.T) {
 	}
 }
 
+func TestSyncWithTrackRenamesStrategyLeaf(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+
+	fs.Config.TrackRenames = true
+	fs.Config.TrackRenamesStrategy = "leaf"
+	defer func() {
+		fs.Config.TrackRenames = false
+		fs.Config.TrackRenamesStrategy = "hash"
+	}()
+
+	canTrackRenames := operations.CanServerSideMove(r.Fremote) && r.Fremote.Precision() != fs.ModTimeNotSupported
+	t.Logf("Can track renames: %v", canTrackRenames)
+
+	f1 := r.WriteFile("potato", "Potato Content", t1)
+	f2 := r.WriteFile("sub/yam", "Yam Content", t2)
+
+	accounting.GlobalStats().ResetCounters()
+	require.NoError(t, Sync(context.Background(), r.Fremote, r.Flocal, false))
+
+	fstest.CheckItems(t, r.Fremote, f1, f2)
+	fstest.CheckItems(t, r.Flocal, f1, f2)
+
+	// Now rename locally.
+	f2 = r.RenameFile(f2, "yam")
+
+	accounting.GlobalStats().ResetCounters()
+	require.NoError(t, Sync(context.Background(), r.Fremote, r.Flocal, false))
+
+	fstest.CheckItems(t, r.Fremote, f1, f2)
+
+	// Check we renamed something if we should have
+	if canTrackRenames {
+		renames := accounting.GlobalStats().Renames(0)
+		assert.Equal(t, canTrackRenames, renames != 0, fmt.Sprintf("canTrackRenames=%v, renames=%d", canTrackRenames, renames))
+	}
+}
+
 func toyFileTransfers(r *fstest.Run) int64 {
 	remote := r.Fremote.Name()
 	transfers := 1