Godeps, vendor: convert dependency management to trash (#3198)

This commit converts the dependency management from Godeps to the vendor
folder, also switching the tool from godep to trash. Since the upstream tool
lacks a few features proposed via a few PRs, until those PRs are merged in
(if), use github.com/karalabe/trash.

You can update dependencies via trash --update.

All dependencies have been updated to their latest version.

Parts of the build system are reworked to drop old notions of Godeps and
invocation of the go vet command so that it doesn't run against the vendor
folder, as that will just blow up during vetting.

The conversion drops OpenCL (and hence GPU mining support) from ethash and our
codebase. The short reasoning is that there's noone to maintain and having
opencl libs in our deps messes up builds as go install ./... tries to build
them, failing with unsatisfied link errors for the C OpenCL deps.

golang.org/x/net/context is not vendored in. We expect it to be fetched by the
user (i.e. using go get). To keep ci.go builds reproducible the package is
"vendored" in build/_vendor.

1 files changed, 300 insertions, 0 deletions

diff --git a/build/_vendor/src/golang.org/x/net/context/pre_go17.go b/build/_vendor/src/golang.org/x/net/context/pre_go17.go
new file mode 100644
index 000000000..5a30acabd
--- /dev/null
+++ b/build/_vendor/src/golang.org/x/net/context/pre_go17.go
@@ -0,0 +1,300 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !go1.7
+
+package context
+
+import (
+	"errors"
+	"fmt"
+	"sync"
+	"time"
+)
+
+// An emptyCtx is never canceled, has no values, and has no deadline.  It is not
+// struct{}, since vars of this type must have distinct addresses.
+type emptyCtx int
+
+func (*emptyCtx) Deadline() (deadline time.Time, ok bool) {
+	return
+}
+
+func (*emptyCtx) Done() <-chan struct{} {
+	return nil
+}
+
+func (*emptyCtx) Err() error {
+	return nil
+}
+
+func (*emptyCtx) Value(key interface{}) interface{} {
+	return nil
+}
+
+func (e *emptyCtx) String() string {
+	switch e {
+	case background:
+		return "context.Background"
+	case todo:
+		return "context.TODO"
+	}
+	return "unknown empty Context"
+}
+
+var (
+	background = new(emptyCtx)
+	todo       = new(emptyCtx)
+)
+
+// Canceled is the error returned by Context.Err when the context is canceled.
+var Canceled = errors.New("context canceled")
+
+// DeadlineExceeded is the error returned by Context.Err when the context's
+// deadline passes.
+var DeadlineExceeded = errors.New("context deadline exceeded")
+
+// WithCancel returns a copy of parent with a new Done channel. The returned
+// context's Done channel is closed when the returned cancel function is called
+// or when the parent context's Done channel is closed, whichever happens first.
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete.
+func WithCancel(parent Context) (ctx Context, cancel CancelFunc) {
+	c := newCancelCtx(parent)
+	propagateCancel(parent, c)
+	return c, func() { c.cancel(true, Canceled) }
+}
+
+// newCancelCtx returns an initialized cancelCtx.
+func newCancelCtx(parent Context) *cancelCtx {
+	return &cancelCtx{
+		Context: parent,
+		done:    make(chan struct{}),
+	}
+}
+
+// propagateCancel arranges for child to be canceled when parent is.
+func propagateCancel(parent Context, child canceler) {
+	if parent.Done() == nil {
+		return // parent is never canceled
+	}
+	if p, ok := parentCancelCtx(parent); ok {
+		p.mu.Lock()
+		if p.err != nil {
+			// parent has already been canceled
+			child.cancel(false, p.err)
+		} else {
+			if p.children == nil {
+				p.children = make(map[canceler]bool)
+			}
+			p.children[child] = true
+		}
+		p.mu.Unlock()
+	} else {
+		go func() {
+			select {
+			case <-parent.Done():
+				child.cancel(false, parent.Err())
+			case <-child.Done():
+			}
+		}()
+	}
+}
+
+// parentCancelCtx follows a chain of parent references until it finds a
+// *cancelCtx.  This function understands how each of the concrete types in this
+// package represents its parent.
+func parentCancelCtx(parent Context) (*cancelCtx, bool) {
+	for {
+		switch c := parent.(type) {
+		case *cancelCtx:
+			return c, true
+		case *timerCtx:
+			return c.cancelCtx, true
+		case *valueCtx:
+			parent = c.Context
+		default:
+			return nil, false
+		}
+	}
+}
+
+// removeChild removes a context from its parent.
+func removeChild(parent Context, child canceler) {
+	p, ok := parentCancelCtx(parent)
+	if !ok {
+		return
+	}
+	p.mu.Lock()
+	if p.children != nil {
+		delete(p.children, child)
+	}
+	p.mu.Unlock()
+}
+
+// A canceler is a context type that can be canceled directly.  The
+// implementations are *cancelCtx and *timerCtx.
+type canceler interface {
+	cancel(removeFromParent bool, err error)
+	Done() <-chan struct{}
+}
+
+// A cancelCtx can be canceled.  When canceled, it also cancels any children
+// that implement canceler.
+type cancelCtx struct {
+	Context
+
+	done chan struct{} // closed by the first cancel call.
+
+	mu       sync.Mutex
+	children map[canceler]bool // set to nil by the first cancel call
+	err      error             // set to non-nil by the first cancel call
+}
+
+func (c *cancelCtx) Done() <-chan struct{} {
+	return c.done
+}
+
+func (c *cancelCtx) Err() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.err
+}
+
+func (c *cancelCtx) String() string {
+	return fmt.Sprintf("%v.WithCancel", c.Context)
+}
+
+// cancel closes c.done, cancels each of c's children, and, if
+// removeFromParent is true, removes c from its parent's children.
+func (c *cancelCtx) cancel(removeFromParent bool, err error) {
+	if err == nil {
+		panic("context: internal error: missing cancel error")
+	}
+	c.mu.Lock()
+	if c.err != nil {
+		c.mu.Unlock()
+		return // already canceled
+	}
+	c.err = err
+	close(c.done)
+	for child := range c.children {
+		// NOTE: acquiring the child's lock while holding parent's lock.
+		child.cancel(false, err)
+	}
+	c.children = nil
+	c.mu.Unlock()
+
+	if removeFromParent {
+		removeChild(c.Context, c)
+	}
+}
+
+// WithDeadline returns a copy of the parent context with the deadline adjusted
+// to be no later than d.  If the parent's deadline is already earlier than d,
+// WithDeadline(parent, d) is semantically equivalent to parent.  The returned
+// context's Done channel is closed when the deadline expires, when the returned
+// cancel function is called, or when the parent context's Done channel is
+// closed, whichever happens first.
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete.
+func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc) {
+	if cur, ok := parent.Deadline(); ok && cur.Before(deadline) {
+		// The current deadline is already sooner than the new one.
+		return WithCancel(parent)
+	}
+	c := &timerCtx{
+		cancelCtx: newCancelCtx(parent),
+		deadline:  deadline,
+	}
+	propagateCancel(parent, c)
+	d := deadline.Sub(time.Now())
+	if d <= 0 {
+		c.cancel(true, DeadlineExceeded) // deadline has already passed
+		return c, func() { c.cancel(true, Canceled) }
+	}
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.err == nil {
+		c.timer = time.AfterFunc(d, func() {
+			c.cancel(true, DeadlineExceeded)
+		})
+	}
+	return c, func() { c.cancel(true, Canceled) }
+}
+
+// A timerCtx carries a timer and a deadline.  It embeds a cancelCtx to
+// implement Done and Err.  It implements cancel by stopping its timer then
+// delegating to cancelCtx.cancel.
+type timerCtx struct {
+	*cancelCtx
+	timer *time.Timer // Under cancelCtx.mu.
+
+	deadline time.Time
+}
+
+func (c *timerCtx) Deadline() (deadline time.Time, ok bool) {
+	return c.deadline, true
+}
+
+func (c *timerCtx) String() string {
+	return fmt.Sprintf("%v.WithDeadline(%s [%s])", c.cancelCtx.Context, c.deadline, c.deadline.Sub(time.Now()))
+}
+
+func (c *timerCtx) cancel(removeFromParent bool, err error) {
+	c.cancelCtx.cancel(false, err)
+	if removeFromParent {
+		// Remove this timerCtx from its parent cancelCtx's children.
+		removeChild(c.cancelCtx.Context, c)
+	}
+	c.mu.Lock()
+	if c.timer != nil {
+		c.timer.Stop()
+		c.timer = nil
+	}
+	c.mu.Unlock()
+}
+
+// WithTimeout returns WithDeadline(parent, time.Now().Add(timeout)).
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete:
+//
+// 	func slowOperationWithTimeout(ctx context.Context) (Result, error) {
+// 		ctx, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
+// 		defer cancel()  // releases resources if slowOperation completes before timeout elapses
+// 		return slowOperation(ctx)
+// 	}
+func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc) {
+	return WithDeadline(parent, time.Now().Add(timeout))
+}
+
+// WithValue returns a copy of parent in which the value associated with key is
+// val.
+//
+// Use context Values only for request-scoped data that transits processes and
+// APIs, not for passing optional parameters to functions.
+func WithValue(parent Context, key interface{}, val interface{}) Context {
+	return &valueCtx{parent, key, val}
+}
+
+// A valueCtx carries a key-value pair.  It implements Value for that key and
+// delegates all other calls to the embedded Context.
+type valueCtx struct {
+	Context
+	key, val interface{}
+}
+
+func (c *valueCtx) String() string {
+	return fmt.Sprintf("%v.WithValue(%#v, %#v)", c.Context, c.key, c.val)
+}
+
+func (c *valueCtx) Value(key interface{}) interface{} {
+	if c.key == key {
+		return c.val
+	}
+	return c.Context.Value(key)
+}