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/dump.go

@@ -0,0 +1,89 @@
+package fs
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+// DumpFlags describes the Dump options in force
+type DumpFlags int
+
+// DumpFlags definitions
+const (
+	DumpHeaders DumpFlags = 1 << iota
+	DumpBodies
+	DumpRequests
+	DumpResponses
+	DumpAuth
+	DumpFilters
+)
+
+var dumpFlags = []struct {
+	flag DumpFlags
+	name string
+}{
+	{DumpHeaders, "headers"},
+	{DumpBodies, "bodies"},
+	{DumpRequests, "requests"},
+	{DumpResponses, "responses"},
+	{DumpAuth, "auth"},
+	{DumpFilters, "filters"},
+}
+
+// DumpFlagsList is a list of dump flags used in the help
+var DumpFlagsList string
+
+func init() {
+	// calculate the dump flags list
+	var out []string
+	for _, info := range dumpFlags {
+		out = append(out, info.name)
+	}
+	DumpFlagsList = strings.Join(out, ",")
+}
+
+// String turns a DumpFlags into a string
+func (f DumpFlags) String() string {
+	var out []string
+	for _, info := range dumpFlags {
+		if f&info.flag != 0 {
+			out = append(out, info.name)
+			f &^= info.flag
+		}
+	}
+	if f != 0 {
+		out = append(out, fmt.Sprintf("Unknown-0x%X", int(f)))
+	}
+	return strings.Join(out, ",")
+}
+
+// Set a DumpFlags as a comma separated list of flags
+func (f *DumpFlags) Set(s string) error {
+	var flags DumpFlags
+	parts := strings.Split(s, ",")
+	for _, part := range parts {
+		found := false
+		part = strings.ToLower(strings.TrimSpace(part))
+		if part == "" {
+			continue
+		}
+		for _, info := range dumpFlags {
+			if part == info.name {
+				found = true
+				flags |= info.flag
+			}
+		}
+		if !found {
+			return errors.Errorf("Unknown dump flag %q", part)
+		}
+	}
+	*f = flags
+	return nil
+}
+
+// Type of the value
+func (f *DumpFlags) Type() string {
+	return "string"
+}