backup: allow excluding online-only cloud files

cmd/restic/cmd_backup.go

@@ -77,6 +77,7 @@ type BackupOptions struct {
 	ExcludeIfPresent  []string
 	ExcludeCaches     bool
 	ExcludeLargerThan string
+	ExcludeCloudFiles bool
 	Stdin             bool
 	StdinFilename     string
 	StdinCommand      bool
@@ -140,6 +141,7 @@ func init() {
 	f.BoolVar(&backupOptions.NoScan, "no-scan", false, "do not run scanner to estimate size of backup")
 	if runtime.GOOS == "windows" {
 		f.BoolVar(&backupOptions.UseFsSnapshot, "use-fs-snapshot", false, "use filesystem snapshot where possible (currently only Windows VSS)")
+		f.BoolVar(&backupOptions.ExcludeCloudFiles, "exclude-cloud-files", false, "excludes online-only cloud files (such as OneDrive Files On-Demand)")
 	}
 	f.BoolVar(&backupOptions.SkipIfUnchanged, "skip-if-unchanged", false, "skip snapshot creation if identical to parent snapshot")
 
@@ -347,6 +349,17 @@ func collectRejectFuncs(opts BackupOptions, targets []string, fs fs.FS) (funcs [
 		funcs = append(funcs, f)
 	}
 
+	if opts.ExcludeCloudFiles && !opts.Stdin && !opts.StdinCommand {
+		if runtime.GOOS != "windows" {
+			return nil, errors.Fatalf("exclude-cloud-files is only supported on Windows")
+		}
+		f, err := archiver.RejectCloudFiles(Warnf)
+		if err != nil {
+			return nil, err
+		}
+		funcs = append(funcs, f)
+	}
+
 	if opts.ExcludeCaches {
 		opts.ExcludeIfPresent = append(opts.ExcludeIfPresent, "CACHEDIR.TAG:Signature: 8a477f597d28d172789f06886806bc55")
 	}