fs: filter flags ability to read from stdin - fixes #4034

fs/filter/filter.go

@@ -465,12 +465,17 @@ func (f *Filter) IncludeObject(ctx context.Context, o fs.Object) bool {
 //
 // It ignores empty lines and lines starting with '#' or ';'
 func forEachLine(path string, fn func(string) error) (err error) {
-	in, err := os.Open(path)
-	if err != nil {
-		return err
+	var scanner *bufio.Scanner
+	if path == "-" {
+		scanner = bufio.NewScanner(os.Stdin)
+	} else {
+		in, err := os.Open(path)
+		if err != nil {
+			return err
+		}
+		scanner = bufio.NewScanner(in)
+		defer fs.CheckClose(in, &err)
 	}
-	defer fs.CheckClose(in, &err)
-	scanner := bufio.NewScanner(in)
 	for scanner.Scan() {
 		line := scanner.Text()
 		line = strings.TrimSpace(line)

fs/filter/filter_test.go

@@ -517,7 +517,7 @@ func TestFilterAddDirRuleOrFileRule(t *testing.T) {
 	}
 }
 
-func TestFilterForEachLine(t *testing.T) {
+func testFilterForEachLine(t *testing.T, useStdin bool) {
 	file := testFile(t, `; comment
 one
 # another comment
@@ -534,7 +534,19 @@ five
 		require.NoError(t, err)
 	}()
 	lines := []string{}
-	err := forEachLine(file, func(s string) error {
+	fileName := file
+	if useStdin {
+		in, err := os.Open(file)
+		require.NoError(t, err)
+		oldStdin := os.Stdin
+		os.Stdin = in
+		defer func() {
+			os.Stdin = oldStdin
+			_ = in.Close()
+		}()
+		fileName = "-"
+	}
+	err := forEachLine(fileName, func(s string) error {
 		lines = append(lines, s)
 		return nil
 	})
@@ -542,6 +554,14 @@ five
 	assert.Equal(t, "one,two,three,four,five,six", strings.Join(lines, ","))
 }
 
+func TestFilterForEachLine(t *testing.T) {
+	testFilterForEachLine(t, false)
+}
+
+func TestFilterForEachLineStdin(t *testing.T) {
+	testFilterForEachLine(t, true)
+}
+
 func TestFilterMatchesFromDocs(t *testing.T) {
 	for _, test := range []struct {
 		glob       string

fs/filter/filterflags/filterflags.go

@@ -24,13 +24,13 @@ func AddFlags(flagSet *pflag.FlagSet) {
 	rc.AddOptionReload("filter", &Opt, Reload)
 	flags.BoolVarP(flagSet, &Opt.DeleteExcluded, "delete-excluded", "", false, "Delete files on dest excluded from sync")
 	flags.StringArrayVarP(flagSet, &Opt.FilterRule, "filter", "f", nil, "Add a file-filtering rule")
-	flags.StringArrayVarP(flagSet, &Opt.FilterFrom, "filter-from", "", nil, "Read filtering patterns from a file")
+	flags.StringArrayVarP(flagSet, &Opt.FilterFrom, "filter-from", "", nil, "Read filtering patterns from a file (use - to read from stdin)")
 	flags.StringArrayVarP(flagSet, &Opt.ExcludeRule, "exclude", "", nil, "Exclude files matching pattern")
-	flags.StringArrayVarP(flagSet, &Opt.ExcludeFrom, "exclude-from", "", nil, "Read exclude patterns from file")
+	flags.StringArrayVarP(flagSet, &Opt.ExcludeFrom, "exclude-from", "", nil, "Read exclude patterns from file (use - to read from stdin)")
 	flags.StringVarP(flagSet, &Opt.ExcludeFile, "exclude-if-present", "", "", "Exclude directories if filename is present")
 	flags.StringArrayVarP(flagSet, &Opt.IncludeRule, "include", "", nil, "Include files matching pattern")
-	flags.StringArrayVarP(flagSet, &Opt.IncludeFrom, "include-from", "", nil, "Read include patterns from file")
-	flags.StringArrayVarP(flagSet, &Opt.FilesFrom, "files-from", "", nil, "Read list of source-file names from file")
+	flags.StringArrayVarP(flagSet, &Opt.IncludeFrom, "include-from", "", nil, "Read include patterns from file (use - to read from stdin)")
+	flags.StringArrayVarP(flagSet, &Opt.FilesFrom, "files-from", "", nil, "Read list of source-file names from file (use - to read from stdin)")
 	flags.FVarP(flagSet, &Opt.MinAge, "min-age", "", "Only transfer files older than this in s or suffix ms|s|m|h|d|w|M|y")
 	flags.FVarP(flagSet, &Opt.MaxAge, "max-age", "", "Only transfer files younger than this in s or suffix ms|s|m|h|d|w|M|y")
 	flags.FVarP(flagSet, &Opt.MinSize, "min-size", "", "Only transfer files bigger than this in k or suffix b|k|M|G")