image prune: remove unused images only with `--all`

Fix a regression in `podman image prune` where unused images were
accidentally removed even when `--all=false`.  Extend and partially
rewrite the e2e tests to make sure we're not regressing again in the
future.

Fixing the aforementioned issue revealed another issue in the default
prune filter.  While prune should remove all "dangling" images (i.e.,
those without tag), it removed only "intermediate" ones; dangling images
without children.  Remove the mistaken comment from the libimage
migration.

Also clarify the help message and man page.

Fixes: #10350
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/test/e2e/prune_test.go b/test/e2e/prune_test.go
index 38f893a43..419748adb 100644
--- a/test/e2e/prune_test.go
+++ b/test/e2e/prune_test.go
@@ -88,6 +88,53 @@ var _ = Describe("Podman prune", func() {
 		Expect(podmanTest.NumberOfContainers()).To(Equal(0))
 	})
 
+	It("podman image prune - remove only dangling images", func() {
+		session := podmanTest.Podman([]string{"images", "-a"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		hasNone, _ := session.GrepString("<none>")
+		Expect(hasNone).To(BeFalse())
+		numImages := len(session.OutputToStringArray())
+
+		// Since there's no dangling image, none should be removed.
+		session = podmanTest.Podman([]string{"image", "prune", "-f"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(len(session.OutputToStringArray())).To(Equal(0))
+
+		// Let's be extra sure that the same number of images is
+		// reported.
+		session = podmanTest.Podman([]string{"images", "-a"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(len(session.OutputToStringArray())).To(Equal(numImages))
+
+		// Now build a new image with dangling intermediate images.
+		podmanTest.BuildImage(pruneImage, "alpine_bash:latest", "true")
+
+		session = podmanTest.Podman([]string{"images", "-a"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		hasNone, _ = session.GrepString("<none>")
+		Expect(hasNone).To(BeTrue()) // ! we have dangling ones
+		numImages = len(session.OutputToStringArray())
+
+		// Since there's at least one dangling image, prune should
+		// remove them.
+		session = podmanTest.Podman([]string{"image", "prune", "-f"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		numPrunedImages := len(session.OutputToStringArray())
+		Expect(numPrunedImages >= 1).To(BeTrue())
+
+		// Now make sure that exactly the number of pruned images has
+		// been removed.
+		session = podmanTest.Podman([]string{"images", "-a"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(len(session.OutputToStringArray())).To(Equal(numImages - numPrunedImages))
+	})
+
 	It("podman image prune skip cache images", func() {
 		podmanTest.BuildImage(pruneImage, "alpine_bash:latest", "true")