Add --latest, -l to 'podman diff'

The man page of 'podman diff' claims that the diff sub-command knows
about --latest, -l. This adds support, as described in the man-page, to
the diff sub-command for --latest, -l.

Signed-off-by: Adrian Reber <areber@redhat.com>

3 files changed, 28 insertions, 2 deletions

diff --git a/cmd/podman/cliconfig/config.go b/cmd/podman/cliconfig/config.go
index 4a4c839cc..e3e2edb95 100644
--- a/cmd/podman/cliconfig/config.go
+++ b/cmd/podman/cliconfig/config.go
@@ -113,6 +113,7 @@ type DiffValues struct {
 	PodmanCommand
 	Archive bool
 	Format  string
+	Latest  bool
 }
 
 type ExecValues struct {
diff --git a/cmd/podman/diff.go b/cmd/podman/diff.go
index 9543113d8..032c0f2c0 100644
--- a/cmd/podman/diff.go
+++ b/cmd/podman/diff.go
@@ -60,8 +60,10 @@ func init() {
 
 	flags.BoolVar(&diffCommand.Archive, "archive", true, "Save the diff as a tar archive")
 	flags.StringVar(&diffCommand.Format, "format", "", "Change the output format")
+	flags.BoolVarP(&diffCommand.Latest, "latest", "l", false, "Act on the latest container podman is aware of")
 
 	flags.MarkHidden("archive")
+	markFlagHiddenForRemoteClient("latest", flags)
 
 }
 
@@ -83,7 +85,7 @@ func formatJSON(output []diffOutputParams) (diffJSONOutput, error) {
 }
 
 func diffCmd(c *cliconfig.DiffValues) error {
-	if len(c.InputArgs) != 1 {
+	if len(c.InputArgs) != 1 && !c.Latest {
 		return errors.Errorf("container, image, or layer name must be specified: podman diff [options [...]] ID-NAME")
 	}
 
@@ -93,7 +95,16 @@ func diffCmd(c *cliconfig.DiffValues) error {
 	}
 	defer runtime.Shutdown(false)
 
-	to := c.InputArgs[0]
+	var to string
+	if c.Latest {
+		ctr, err := runtime.GetLatestContainer()
+		if err != nil {
+			return errors.Wrapf(err, "unable to get latest container")
+		}
+		to = ctr.ID()
+	} else {
+		to = c.InputArgs[0]
+	}
 	changes, err := runtime.Diff(c, to)
 	if err != nil {
 		return errors.Wrapf(err, "could not get changes for %q", to)
diff --git a/test/e2e/diff_test.go b/test/e2e/diff_test.go
index 0f53d9bc8..d273f9463 100644
--- a/test/e2e/diff_test.go
+++ b/test/e2e/diff_test.go
@@ -80,4 +80,18 @@ var _ = Describe("Podman diff", func() {
 		sort.Strings(imageDiff)
 		Expect(imageDiff).To(Equal(containerDiff))
 	})
+
+	It("podman diff latest container", func() {
+		SkipIfRemote()
+		session := podmanTest.Podman([]string{"run", "--name=diff-test", ALPINE, "touch", "/tmp/diff-test"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		session = podmanTest.Podman([]string{"diff", "-l"})
+		session.WaitWithDefaultTimeout()
+		containerDiff := session.OutputToStringArray()
+		sort.Strings(containerDiff)
+		Expect(session.LineInOutputContains("C /tmp")).To(BeTrue())
+		Expect(session.LineInOutputContains("A /tmp/diff-test")).To(BeTrue())
+		Expect(session.ExitCode()).To(Equal(0))
+	})
 })