Implement new backend config system

This unifies the 3 methods of reading config

  * command line
  * environment variable
  * config file

And allows them all to be configured in all places.  This is done by
making the []fs.Option in the backend registration be the master
source of what the backend options are.

The backend changes are:

  * Use the new configmap.Mapper parameter
  * Use configstruct to parse it into an Options struct
  * Add all config to []fs.Option including defaults and help
  * Remove all uses of pflag
  * Remove all uses of config.FileGet

cmd/cmd.go

@@ -16,6 +16,7 @@ import (
 	"runtime"
 	"runtime/pprof"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/pkg/errors"
@@ -151,12 +152,12 @@ func ShowVersion() {
 // It returns a string with the file name if points to a file
 // otherwise "".
 func NewFsFile(remote string) (fs.Fs, string) {
-	fsInfo, configName, fsPath, err := fs.ParseRemote(remote)
+	_, _, fsPath, err := fs.ParseRemote(remote)
 	if err != nil {
 		fs.CountError(err)
 		log.Fatalf("Failed to create file system for %q: %v", remote, err)
 	}
-	f, err := fsInfo.NewFs(configName, fsPath)
+	f, err := fs.NewFs(remote)
 	switch err {
 	case fs.ErrorIsFile:
 		return f, path.Base(fsPath)
@@ -496,3 +497,51 @@ func resolveExitCode(err error) {
 		os.Exit(exitCodeUsageError)
 	}
 }
+
+// AddBackendFlags creates flags for all the backend options
+func AddBackendFlags() {
+	for _, fsInfo := range fs.Registry {
+		done := map[string]struct{}{}
+		for i := range fsInfo.Options {
+			opt := &fsInfo.Options[i]
+			// Skip if done already (eg with Provider options)
+			if _, doneAlready := done[opt.Name]; doneAlready {
+				continue
+			}
+			done[opt.Name] = struct{}{}
+			// Make a flag from each option
+			name := strings.Replace(opt.Name, "_", "-", -1) // convert snake_case to kebab-case
+			if !opt.NoPrefix {
+				name = fsInfo.Prefix + "-" + name
+			}
+			found := pflag.CommandLine.Lookup(name) != nil
+			if !found {
+				// Take first line of help only
+				help := strings.TrimSpace(opt.Help)
+				if nl := strings.IndexRune(help, '\n'); nl >= 0 {
+					help = help[:nl]
+				}
+				help = strings.TrimSpace(help)
+				flag := pflag.CommandLine.VarPF(opt, name, string(opt.ShortOpt), help)
+				if _, isBool := opt.Value.(bool); isBool {
+					flag.NoOptDefVal = "true"
+				}
+				// Hide on the command line if requested
+				if opt.Hide&fs.OptionHideCommandLine != 0 {
+					flag.Hidden = true
+				}
+			} else {
+				fs.Errorf(nil, "Not adding duplicate flag --%s", name)
+			}
+			//flag.Hidden = true
+		}
+	}
+}
+
+// Main runs rclone interpreting flags and commands out of os.Args
+func Main() {
+	AddBackendFlags()
+	if err := Root.Execute(); err != nil {
+		log.Fatalf("Fatal error: %v", err)
+	}
+}