copy: add a --all/-a flag

Add a --all/-a flag to instruct us to attempt to copy all of the
instances in the source image, if the source image specified to "skopeo
copy" is actually a list of images.  Previously, we'd just try to locate
one for our preferred OS/arch combination.

Add a couple of tests to verify that we can copy an image into and then
back out of containers-storage.  The contents of an image that has been
copied out of containers-storage need a bit of tweaking to compensate
for containers-storage's habit of returning uncompressed versions of the
layer blobs that were originally written to it, in order to be
comparable to the image as it was when it was pulled from a registry.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

integration/utils.go

@@ -6,6 +6,7 @@ import (
 	"io/ioutil"
 	"net"
 	"os/exec"
+	"path/filepath"
 	"strings"
 	"time"
 
@@ -13,6 +14,7 @@ import (
 )
 
 const skopeoBinary = "skopeo"
+const decompressDirsBinary = "./decompress-dirs.sh"
 
 // consumeAndLogOutputStream takes (f, err) from an exec.*Pipe(), and causes all output to it to be logged to c.
 func consumeAndLogOutputStream(c *check.C, id string, f io.ReadCloser, err error) {
@@ -174,3 +176,27 @@ func fileFromFixture(c *check.C, inputPath string, edits map[string]string) stri
 	c.Assert(err, check.IsNil)
 	return path
 }
+
+// runDecompressDirs runs decompress-dirs.sh using exec.Command().CombinedOutput, verifies that the exit status is 0,
+// and optionally that the output matches a multi-line regexp if it is nonempty; or terminates c on failure
+func runDecompressDirs(c *check.C, regexp string, args ...string) {
+	c.Logf("Running %s %s", decompressDirsBinary, strings.Join(args, " "))
+	for i, dir := range args {
+		m, err := ioutil.ReadFile(filepath.Join(dir, "manifest.json"))
+		c.Assert(err, check.IsNil)
+		c.Logf("manifest %d before: %s", i+1, string(m))
+	}
+	out, err := exec.Command(decompressDirsBinary, args...).CombinedOutput()
+	c.Assert(err, check.IsNil, check.Commentf("%s", out))
+	for i, dir := range args {
+		if len(out) > 0 {
+			c.Logf("output: %s", out)
+		}
+		m, err := ioutil.ReadFile(filepath.Join(dir, "manifest.json"))
+		c.Assert(err, check.IsNil)
+		c.Logf("manifest %d after: %s", i+1, string(m))
+	}
+	if regexp != "" {
+		c.Assert(string(out), check.Matches, "(?s)"+regexp) // (?s) : '.' will also match newlines
+	}
+}