Implement Cobra CLI tooling, Viper config tooling (#336)

* start pulling out + replacing urfave and config

* replace many many instances of config

* move more stuff => viper

* properly remove urfave

* move some flags to root command

* add testrig commands to root

* alias config file keys

* start adding cli parsing tests

* reorder viper init

* remove config path alias

* fmt

* change config file keys to non-nested

* we're more or less in business now

* tidy up the common func

* go fmt

* get tests passing again

* add note about the cliparsing tests

* reorganize

* update docs with changes

* structure cmd dir better

* rename + move some files around

* fix dangling comma

vendor/github.com/spf13/cobra/args.go

@@ -0,0 +1,109 @@
+package cobra
+
+import (
+	"fmt"
+	"strings"
+)
+
+type PositionalArgs func(cmd *Command, args []string) error
+
+// Legacy arg validation has the following behaviour:
+// - root commands with no subcommands can take arbitrary arguments
+// - root commands with subcommands will do subcommand validity checking
+// - subcommands will always accept arbitrary arguments
+func legacyArgs(cmd *Command, args []string) error {
+	// no subcommand, always take args
+	if !cmd.HasSubCommands() {
+		return nil
+	}
+
+	// root command with subcommands, do subcommand checking.
+	if !cmd.HasParent() && len(args) > 0 {
+		return fmt.Errorf("unknown command %q for %q%s", args[0], cmd.CommandPath(), cmd.findSuggestions(args[0]))
+	}
+	return nil
+}
+
+// NoArgs returns an error if any args are included.
+func NoArgs(cmd *Command, args []string) error {
+	if len(args) > 0 {
+		return fmt.Errorf("unknown command %q for %q", args[0], cmd.CommandPath())
+	}
+	return nil
+}
+
+// OnlyValidArgs returns an error if any args are not in the list of ValidArgs.
+func OnlyValidArgs(cmd *Command, args []string) error {
+	if len(cmd.ValidArgs) > 0 {
+		// Remove any description that may be included in ValidArgs.
+		// A description is following a tab character.
+		var validArgs []string
+		for _, v := range cmd.ValidArgs {
+			validArgs = append(validArgs, strings.Split(v, "\t")[0])
+		}
+
+		for _, v := range args {
+			if !stringInSlice(v, validArgs) {
+				return fmt.Errorf("invalid argument %q for %q%s", v, cmd.CommandPath(), cmd.findSuggestions(args[0]))
+			}
+		}
+	}
+	return nil
+}
+
+// ArbitraryArgs never returns an error.
+func ArbitraryArgs(cmd *Command, args []string) error {
+	return nil
+}
+
+// MinimumNArgs returns an error if there is not at least N args.
+func MinimumNArgs(n int) PositionalArgs {
+	return func(cmd *Command, args []string) error {
+		if len(args) < n {
+			return fmt.Errorf("requires at least %d arg(s), only received %d", n, len(args))
+		}
+		return nil
+	}
+}
+
+// MaximumNArgs returns an error if there are more than N args.
+func MaximumNArgs(n int) PositionalArgs {
+	return func(cmd *Command, args []string) error {
+		if len(args) > n {
+			return fmt.Errorf("accepts at most %d arg(s), received %d", n, len(args))
+		}
+		return nil
+	}
+}
+
+// ExactArgs returns an error if there are not exactly n args.
+func ExactArgs(n int) PositionalArgs {
+	return func(cmd *Command, args []string) error {
+		if len(args) != n {
+			return fmt.Errorf("accepts %d arg(s), received %d", n, len(args))
+		}
+		return nil
+	}
+}
+
+// ExactValidArgs returns an error if
+// there are not exactly N positional args OR
+// there are any positional args that are not in the `ValidArgs` field of `Command`
+func ExactValidArgs(n int) PositionalArgs {
+	return func(cmd *Command, args []string) error {
+		if err := ExactArgs(n)(cmd, args); err != nil {
+			return err
+		}
+		return OnlyValidArgs(cmd, args)
+	}
+}
+
+// RangeArgs returns an error if the number of args is not within the expected range.
+func RangeArgs(min int, max int) PositionalArgs {
+	return func(cmd *Command, args []string) error {
+		if len(args) < min || len(args) > max {
+			return fmt.Errorf("accepts between %d and %d arg(s), received %d", min, max, len(args))
+		}
+		return nil
+	}
+}