Run (make vendor) for the first time.

This primarily adds vendor/github.com/containers/image/docs/ ,
but also updates other dependencies that are not pinned to a specific
commit.

vendor/golang.org/x/net/http2/write.go

@@ -11,8 +11,8 @@ import (
 	"net/http"
 	"net/url"
 
+	"golang.org/x/net/http/httpguts"
 	"golang.org/x/net/http2/hpack"
-	"golang.org/x/net/lex/httplex"
 )
 
 // writeFramer is implemented by any type that is used to write frames.
@@ -186,6 +186,7 @@ type writeResHeaders struct {
 	date          string
 	contentType   string
 	contentLength string
+	noSniff       bool
 }
 
 func encKV(enc *hpack.Encoder, k, v string) {
@@ -222,6 +223,9 @@ func (w *writeResHeaders) writeFrame(ctx writeContext) error {
 	if w.contentLength != "" {
 		encKV(enc, "content-length", w.contentLength)
 	}
+	if w.noSniff {
+		encKV(enc, "x-content-type-options", "nosniff")
+	}
 	if w.date != "" {
 		encKV(enc, "date", w.date)
 	}
@@ -350,7 +354,7 @@ func encodeHeaders(enc *hpack.Encoder, h http.Header, keys []string) {
 		}
 		isTE := k == "transfer-encoding"
 		for _, v := range vv {
-			if !httplex.ValidHeaderFieldValue(v) {
+			if !httpguts.ValidHeaderFieldValue(v) {
 				// TODO: return an error? golang.org/issue/14048
 				// For now just omit it.
 				continue