vendor: add sourcegraph/s3cache and dependencies

Adds:
 - github.com/kr/http/transport
 - github.com/sqs/s3
 - github.com/sqs/s3/s3util
 - sourcegraph.com/sourcegraph/s3cache

vendor/github.com/kr/http/transport/AUTHORS

@@ -0,0 +1,3 @@
+# This source code refers to The Go Authors for copyright purposes.
+# The master list of authors is in the main Go distribution,
+# visible at http://tip.golang.org/AUTHORS.

vendor/github.com/kr/http/transport/CONTRIBUTORS

@@ -0,0 +1,3 @@
+# This source code was written by the Go contributors.
+# The master list of contributors is in the main Go distribution,
+# visible at http://tip.golang.org/CONTRIBUTORS.

vendor/github.com/kr/http/transport/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The transport Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/github.com/kr/http/transport/Readme

@@ -0,0 +1,4 @@
+package transport contains a generic wrapper for http.RoundTripper
+
+It was shamelessly copied (slightly modified) from
+https://github.com/golang/oauth2/blob/95a9f97e5/transport.go

vendor/github.com/kr/http/transport/transport.go

@@ -0,0 +1,132 @@
+// Copyright 2014 The transport Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package transport provides a general-purpose wapper for
+// http.RoundTripper. It implements the pattern of taking a
+// request, modifying a copy, and passing the modified copy to an
+// underlying RoundTripper, including bookkeeping necessary to
+// cancel in-flight requests.
+package transport
+
+import (
+	"errors"
+	"io"
+	"net/http"
+	"sync"
+)
+
+// Wrapper is an http.RoundTripper that makes HTTP requests,
+// wrapping a base RoundTripper and altering every outgoing
+// request in some way.
+type Wrapper struct {
+	// Modify alters the request as needed.
+	Modify func(*http.Request) error
+
+	// Base is the base RoundTripper used to make HTTP requests.
+	// If nil, http.DefaultTransport is used.
+	Base http.RoundTripper
+
+	mu     sync.Mutex                      // guards modReq
+	modReq map[*http.Request]*http.Request // original -> modified
+}
+
+// RoundTrip provides a copy of req
+// to the underlying RoundTripper,
+// altered in some way by Modify.
+func (t *Wrapper) RoundTrip(req *http.Request) (*http.Response, error) {
+	if t.Modify == nil {
+		return nil, errors.New("transport: Wrapper's Modify is nil")
+	}
+
+	req2 := cloneRequest(req) // per RoundTripper contract
+	err := t.Modify(req2)
+	if err != nil {
+		return nil, err
+	}
+	t.setModReq(req, req2)
+	res, err := t.base().RoundTrip(req2)
+	if err != nil {
+		t.setModReq(req, nil)
+		return nil, err
+	}
+	res.Body = &onEOFReader{
+		rc: res.Body,
+		fn: func() { t.setModReq(req, nil) },
+	}
+	return res, nil
+}
+
+// CancelRequest cancels an in-flight request by closing its connection.
+func (t *Wrapper) CancelRequest(req *http.Request) {
+	type canceler interface {
+		CancelRequest(*http.Request)
+	}
+	if cr, ok := t.base().(canceler); ok {
+		t.mu.Lock()
+		modReq := t.modReq[req]
+		delete(t.modReq, req)
+		t.mu.Unlock()
+		cr.CancelRequest(modReq)
+	}
+}
+
+func (t *Wrapper) base() http.RoundTripper {
+	if t.Base != nil {
+		return t.Base
+	}
+	return http.DefaultTransport
+}
+
+func (t *Wrapper) setModReq(orig, mod *http.Request) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.modReq == nil {
+		t.modReq = make(map[*http.Request]*http.Request)
+	}
+	if mod == nil {
+		delete(t.modReq, orig)
+	} else {
+		t.modReq[orig] = mod
+	}
+}
+
+// cloneRequest returns a clone of the provided *http.Request.
+// The clone is a shallow copy of the struct and its Header map.
+func cloneRequest(r *http.Request) *http.Request {
+	// shallow copy of the struct
+	r2 := new(http.Request)
+	*r2 = *r
+	// deep copy of the Header
+	r2.Header = make(http.Header, len(r.Header))
+	for k, s := range r.Header {
+		r2.Header[k] = append([]string(nil), s...)
+	}
+	return r2
+}
+
+type onEOFReader struct {
+	rc io.ReadCloser
+	fn func()
+}
+
+func (r *onEOFReader) Read(p []byte) (n int, err error) {
+	n, err = r.rc.Read(p)
+	if err == io.EOF {
+		r.runFunc()
+	}
+	return
+}
+
+func (r *onEOFReader) Close() error {
+	err := r.rc.Close()
+	r.runFunc()
+	return err
+}
+
+func (r *onEOFReader) runFunc() {
+	if fn := r.fn; fn != nil {
+		fn()
+		r.fn = nil
+	}
+}