Break the fs package up into smaller parts.

The purpose of this is to make it easier to maintain and eventually to
allow the rclone backends to be re-used in other projects without
having to use the rclone configuration system.

The new code layout is documented in CONTRIBUTING.

fs/parseduration_test.go

@@ -0,0 +1,44 @@
+package fs
+
+import (
+	"testing"
+	"time"
+
+	"github.com/spf13/pflag"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// Check it satisfies the interface
+var _ pflag.Value = (*Duration)(nil)
+
+func TestParseDuration(t *testing.T) {
+	for _, test := range []struct {
+		in   string
+		want float64
+		err  bool
+	}{
+		{"0", 0, false},
+		{"", 0, true},
+		{"1ms", float64(time.Millisecond), false},
+		{"1s", float64(time.Second), false},
+		{"1m", float64(time.Minute), false},
+		{"1h", float64(time.Hour), false},
+		{"1d", float64(time.Hour) * 24, false},
+		{"1w", float64(time.Hour) * 24 * 7, false},
+		{"1M", float64(time.Hour) * 24 * 30, false},
+		{"1y", float64(time.Hour) * 24 * 365, false},
+		{"1.5y", float64(time.Hour) * 24 * 365 * 1.5, false},
+		{"-1s", -float64(time.Second), false},
+		{"1.s", float64(time.Second), false},
+		{"1x", 0, true},
+	} {
+		duration, err := ParseDuration(test.in)
+		if test.err {
+			require.Error(t, err)
+		} else {
+			require.NoError(t, err)
+		}
+		assert.Equal(t, test.want, float64(duration))
+	}
+}