Update dependencies, enable pruning for vendor/

So, `dep` got an nice new feature to remove tests and non-go files from
`vendor/`, and this brings the size of the vendor directory from ~300MiB
down to ~20MiB. We don that now.

vendor/github.com/pkg/sftp/request.go

@@ -152,9 +152,11 @@ func (r *Request) getLister() ListerAt {
 
 // Close reader/writer if possible
 func (r *Request) close() error {
-	if r.cancelCtx != nil {
-		r.cancelCtx()
-	}
+	defer func() {
+		if r.cancelCtx != nil {
+			r.cancelCtx()
+		}
+	}()
 	rd := r.getReader()
 	if c, ok := rd.(io.Closer); ok {
 		return c.Close()
@@ -175,8 +177,10 @@ func (r *Request) call(handlers Handlers, pkt requestPacket) responsePacket {
 		return fileput(handlers.FilePut, r, pkt)
 	case "Setstat", "Rename", "Rmdir", "Mkdir", "Symlink", "Remove":
 		return filecmd(handlers.FileCmd, r, pkt)
-	case "List", "Stat", "Readlink":
+	case "List":
 		return filelist(handlers.FileList, r, pkt)
+	case "Stat", "Readlink":
+		return filestat(handlers.FileList, r, pkt)
 	default:
 		return statusFromError(pkt,
 			errors.Errorf("unexpected method: %s", r.Method))
@@ -242,6 +246,12 @@ func fileput(h FileWriter, r *Request, pkt requestPacket) responsePacket {
 
 // wrap FileCmder handler
 func filecmd(h FileCmder, r *Request, pkt requestPacket) responsePacket {
+
+	switch p := pkt.(type) {
+	case *sshFxpFsetstatPacket:
+		r.Flags = p.Flags
+		r.Attrs = p.Attrs.([]byte)
+	}
 	err := h.Filecmd(r)
 	return statusFromError(pkt, err)
 }
@@ -270,7 +280,7 @@ func filelist(h FileLister, r *Request, pkt requestPacket) responsePacket {
 		if err != nil && err != io.EOF {
 			return statusFromError(pkt, err)
 		}
-		if n == 0 {
+		if err == io.EOF && n == 0 {
 			return statusFromError(pkt, io.EOF)
 		}
 		dirname := filepath.ToSlash(path.Base(r.Filepath))
@@ -284,6 +294,22 @@ func filelist(h FileLister, r *Request, pkt requestPacket) responsePacket {
 			})
 		}
 		return ret
+	default:
+		err = errors.Errorf("unexpected method: %s", r.Method)
+		return statusFromError(pkt, err)
+	}
+}
+
+func filestat(h FileLister, r *Request, pkt requestPacket) responsePacket {
+	lister, err := h.Filelist(r)
+	if err != nil {
+		return statusFromError(pkt, err)
+	}
+	finfo := make([]os.FileInfo, 1)
+	n, err := lister.ListAt(finfo, 0)
+	finfo = finfo[:n] // avoid need for nil tests below
+
+	switch r.Method {
 	case "Stat":
 		if err != nil && err != io.EOF {
 			return statusFromError(pkt, err)
@@ -330,8 +356,10 @@ func requestMethod(p requestPacket) (method string) {
 		method = "Put"
 	case *sshFxpReaddirPacket:
 		method = "List"
-	case *sshFxpOpenPacket, *sshFxpOpendirPacket:
+	case *sshFxpOpenPacket:
 		method = "Open"
+	case *sshFxpOpendirPacket:
+		method = "Stat"
 	case *sshFxpSetstatPacket, *sshFxpFsetstatPacket:
 		method = "Setstat"
 	case *sshFxpRenamePacket: