Delete vendored code and update CI to Go 1.13 (#158)

As the Go community transitions to using the modules ecosystem,
we want to only support one way of managing dependencies.
So this change moves to only using Go modules for dependency management.

This means that our effective minimum Go version increases to Go 1.11.
To account for this, we also update:
  - the documentation
  - Makefile
  - CI scripts

1 files changed, 0 insertions, 115 deletions

diff --git a/vendor/github.com/urfave/cli/errors.go b/vendor/github.com/urfave/cli/errors.go
deleted file mode 100644
index 562b295..0000000
--- a/vendor/github.com/urfave/cli/errors.go
+++ /dev/null
@@ -1,115 +0,0 @@
-package cli
-
-import (
-	"fmt"
-	"io"
-	"os"
-	"strings"
-)
-
-// OsExiter is the function used when the app exits. If not set defaults to os.Exit.
-var OsExiter = os.Exit
-
-// ErrWriter is used to write errors to the user. This can be anything
-// implementing the io.Writer interface and defaults to os.Stderr.
-var ErrWriter io.Writer = os.Stderr
-
-// MultiError is an error that wraps multiple errors.
-type MultiError struct {
-	Errors []error
-}
-
-// NewMultiError creates a new MultiError. Pass in one or more errors.
-func NewMultiError(err ...error) MultiError {
-	return MultiError{Errors: err}
-}
-
-// Error implements the error interface.
-func (m MultiError) Error() string {
-	errs := make([]string, len(m.Errors))
-	for i, err := range m.Errors {
-		errs[i] = err.Error()
-	}
-
-	return strings.Join(errs, "\n")
-}
-
-type ErrorFormatter interface {
-	Format(s fmt.State, verb rune)
-}
-
-// ExitCoder is the interface checked by `App` and `Command` for a custom exit
-// code
-type ExitCoder interface {
-	error
-	ExitCode() int
-}
-
-// ExitError fulfills both the builtin `error` interface and `ExitCoder`
-type ExitError struct {
-	exitCode int
-	message  interface{}
-}
-
-// NewExitError makes a new *ExitError
-func NewExitError(message interface{}, exitCode int) *ExitError {
-	return &ExitError{
-		exitCode: exitCode,
-		message:  message,
-	}
-}
-
-// Error returns the string message, fulfilling the interface required by
-// `error`
-func (ee *ExitError) Error() string {
-	return fmt.Sprintf("%v", ee.message)
-}
-
-// ExitCode returns the exit code, fulfilling the interface required by
-// `ExitCoder`
-func (ee *ExitError) ExitCode() int {
-	return ee.exitCode
-}
-
-// HandleExitCoder checks if the error fulfills the ExitCoder interface, and if
-// so prints the error to stderr (if it is non-empty) and calls OsExiter with the
-// given exit code.  If the given error is a MultiError, then this func is
-// called on all members of the Errors slice and calls OsExiter with the last exit code.
-func HandleExitCoder(err error) {
-	if err == nil {
-		return
-	}
-
-	if exitErr, ok := err.(ExitCoder); ok {
-		if err.Error() != "" {
-			if _, ok := exitErr.(ErrorFormatter); ok {
-				fmt.Fprintf(ErrWriter, "%+v\n", err)
-			} else {
-				fmt.Fprintln(ErrWriter, err)
-			}
-		}
-		OsExiter(exitErr.ExitCode())
-		return
-	}
-
-	if multiErr, ok := err.(MultiError); ok {
-		code := handleMultiError(multiErr)
-		OsExiter(code)
-		return
-	}
-}
-
-func handleMultiError(multiErr MultiError) int {
-	code := 1
-	for _, merr := range multiErr.Errors {
-		if multiErr2, ok := merr.(MultiError); ok {
-			code = handleMultiError(multiErr2)
-		} else {
-			fmt.Fprintln(ErrWriter, merr)
-			if exitErr, ok := merr.(ExitCoder); ok {
-				code = exitErr.ExitCode()
-			}
-		}
-	}
-	return code
-}