A take is a comparison: the host's facts, former targets, and strays (hq ADR 0163)

Every held thing carries what a take compares: for a found container its image and the image's date,
the networks it is on and the other containers on each, its mounts and published ports, beside the
declared image (and its date once pulled), ports and volumes, with the downgrade decided when both
dates are known; for a found file whether the declared content differs and how, as lines lost and
lines new. A resource whose target moved keeps the former target on record as an orphan, so the next
apply removes the container or file the host wrote under the old name (issue 097). Every apply reports
the strays: containers the mesh neither wrote nor holds.

internal/apply/hold_test.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 	"testing"
 
@@ -18,7 +19,11 @@ import (
 // label when a host made it. Every command it is asked is written down.
 type machine struct {
 	containers map[string]*fakeContainer
-	asked      []string
+	// images is what `image inspect --format {{.Created}}` answers per image or id; members is
+	// what `network inspect` lists per network (ADR 0163).
+	images  map[string]string
+	members map[string][]string
+	asked   []string
 	// wgUp is what `wg show interfaces` answers: the tunnels up on the machine.
 	wgUp string
 	// handshakes is what `wg show <interface> latest-handshakes` answers, and handshakesFail the
@@ -97,6 +102,9 @@ type fakeContainer struct {
 	id      string
 	running bool
 	spec    string
+	// What a take compares (ADR 0163), answered in the long inspect form when set.
+	image, imageID          string
+	networks, mounts, ports []string
 }
 
 func (m *machine) run(_ context.Context, name string, args ...string) (string, error) {
@@ -140,9 +148,38 @@ func (m *machine) run(_ context.Context, name string, args ...string) (string, e
 			running = "true"
 		}
 		if strings.HasPrefix(args[3], "{{.Id}}") {
-			return c.id + "\t" + running + "\t" + c.spec + "\n", nil
+			line := c.id + "\t" + running + "\t" + c.spec
+			if c.image != "" {
+				line += "\t" + c.image + "\t" + c.imageID + "\t" + strings.Join(c.networks, ",") + "," +
+					"\t" + strings.Join(c.mounts, ",") + "," + "\t" + strings.Join(c.ports, ",") + ","
+			}
+			return line + "\n", nil
 		}
 		return running + "\t" + c.spec + "\n", nil
+	case "image":
+		if len(args) > 1 && args[1] == "inspect" {
+			if created, ok := m.images[args[len(args)-1]]; ok {
+				return created + "\n", nil
+			}
+			return "", errors.New("no such image")
+		}
+		return "", nil
+	case "network":
+		if len(args) > 1 && args[1] == "inspect" {
+			return strings.Join(m.members[args[len(args)-1]], ",") + ",\n", nil
+		}
+		return "", nil
+	case "ps":
+		var lines []string
+		for name, c := range m.containers {
+			state := "exited"
+			if c.running {
+				state = "running"
+			}
+			lines = append(lines, name+"\t"+c.image+"\t"+state)
+		}
+		sort.Strings(lines)
+		return strings.Join(lines, "\n") + "\n", nil
 	case "rm":
 		delete(m.containers, args[len(args)-1])
 		return "", nil