features: add basic feature flag implementation

cmd/restic/cmd_features.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/feature"
+	"github.com/restic/restic/internal/ui/table"
+
+	"github.com/spf13/cobra"
+)
+
+// FIXME explain semantics
+
+var featuresCmd = &cobra.Command{
+	Use:   "features",
+	Short: "Print list of feature flags",
+	Long: `
+The "features" command prints a list of supported feature flags.
+
+EXIT STATUS
+===========
+
+Exit status is 0 if the command was successful, and non-zero if there was any error.
+`,
+	Hidden:            true,
+	DisableAutoGenTag: true,
+	RunE: func(_ *cobra.Command, args []string) error {
+		if len(args) != 0 {
+			return errors.Fatal("the feature command expects no arguments")
+		}
+
+		fmt.Printf("All Feature Flags:\n")
+		flags := feature.Flag.List()
+
+		tab := table.New()
+		tab.AddColumn("Name", "{{ .Name }}")
+		tab.AddColumn("Type", "{{ .Type }}")
+		tab.AddColumn("Default", "{{ .Default }}")
+		tab.AddColumn("Description", "{{ .Description }}")
+
+		for _, flag := range flags {
+			tab.AddRow(flag)
+		}
+		return tab.Write(globalOptions.stdout)
+	},
+}
+
+func init() {
+	cmdRoot.AddCommand(featuresCmd)
+}