new "image" mount type

Add a new "image" mount type to `--mount`.  The source of the mount is
the name or ID of an image.  The destination is the path inside the
container.  Image mounts further support an optional `rw,readwrite`
parameter which if set to "true" will yield the mount writable inside
the container.  Note that no changes are propagated to the image mount
on the host (which in any case is read only).

Mounts are overlay mounts.  To support read-only overlay mounts, vendor
a non-release version of Buildah.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

vendor/github.com/prometheus/procfs/arp.go

@@ -1,85 +0,0 @@
-// Copyright 2019 The Prometheus Authors
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package procfs
-
-import (
-	"fmt"
-	"io/ioutil"
-	"net"
-	"strings"
-)
-
-// ARPEntry contains a single row of the columnar data represented in
-// /proc/net/arp.
-type ARPEntry struct {
-	// IP address
-	IPAddr net.IP
-	// MAC address
-	HWAddr net.HardwareAddr
-	// Name of the device
-	Device string
-}
-
-// GatherARPEntries retrieves all the ARP entries, parse the relevant columns,
-// and then return a slice of ARPEntry's.
-func (fs FS) GatherARPEntries() ([]ARPEntry, error) {
-	data, err := ioutil.ReadFile(fs.proc.Path("net/arp"))
-	if err != nil {
-		return nil, fmt.Errorf("error reading arp %s: %s", fs.proc.Path("net/arp"), err)
-	}
-
-	return parseARPEntries(data)
-}
-
-func parseARPEntries(data []byte) ([]ARPEntry, error) {
-	lines := strings.Split(string(data), "\n")
-	entries := make([]ARPEntry, 0)
-	var err error
-	const (
-		expectedDataWidth   = 6
-		expectedHeaderWidth = 9
-	)
-	for _, line := range lines {
-		columns := strings.Fields(line)
-		width := len(columns)
-
-		if width == expectedHeaderWidth || width == 0 {
-			continue
-		} else if width == expectedDataWidth {
-			entry, err := parseARPEntry(columns)
-			if err != nil {
-				return []ARPEntry{}, fmt.Errorf("failed to parse ARP entry: %s", err)
-			}
-			entries = append(entries, entry)
-		} else {
-			return []ARPEntry{}, fmt.Errorf("%d columns were detected, but %d were expected", width, expectedDataWidth)
-		}
-
-	}
-
-	return entries, err
-}
-
-func parseARPEntry(columns []string) (ARPEntry, error) {
-	ip := net.ParseIP(columns[0])
-	mac := net.HardwareAddr(columns[3])
-
-	entry := ARPEntry{
-		IPAddr: ip,
-		HWAddr: mac,
-		Device: columns[5],
-	}
-
-	return entry, nil
-}