Add darwin support for remote-client

Add the ability to cross-compile podman remote for OSX.

Also, add image exists and tag to remote-client.

Signed-off-by: baude <bbaude@redhat.com>

libpod/container_api.go

@@ -3,6 +3,7 @@ package libpod
 import (
 	"context"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"os"
 	"strconv"
@@ -413,6 +414,25 @@ func (c *Container) Exec(tty, privileged bool, env, cmd []string, user, workDir
 	return waitErr
 }
 
+// AttachStreams contains streams that will be attached to the container
+type AttachStreams struct {
+	// OutputStream will be attached to container's STDOUT
+	OutputStream io.WriteCloser
+	// ErrorStream will be attached to container's STDERR
+	ErrorStream io.WriteCloser
+	// InputStream will be attached to container's STDIN
+	InputStream io.Reader
+	// AttachOutput is whether to attach to STDOUT
+	// If false, stdout will not be attached
+	AttachOutput bool
+	// AttachError is whether to attach to STDERR
+	// If false, stdout will not be attached
+	AttachError bool
+	// AttachInput is whether to attach to STDIN
+	// If false, stdout will not be attached
+	AttachInput bool
+}
+
 // Attach attaches to a container
 func (c *Container) Attach(streams *AttachStreams, keys string, resize <-chan remotecommand.TerminalSize) error {
 	if !c.batched {