podman diff accept two images or containers

First, make podman diff accept optionally a second argument. This allows
the user to specify a second image/container to compare the first with.
If it is not set the parent layer will be used as before.

Second, podman container diff should only use containers and podman
image diff should only use images. Previously, podman container diff
would use the image when both an image and container with this name
exists.

To make this work two new parameters have been added to the api. If they
are not used the previous behaviour is used. The same applies to the
bindings.

Fixes #10649

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

3 files changed, 52 insertions, 20 deletions

diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index 25db3cff0..850af235f 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -923,7 +923,7 @@ func (c *Container) exportCheckpoint(options ContainerCheckpointOptions) error {
 	var addToTarFiles []string
 	if !options.IgnoreRootfs {
 		// To correctly track deleted files, let's go through the output of 'podman diff'
-		rootFsChanges, err := c.runtime.GetDiff("", c.ID())
+		rootFsChanges, err := c.runtime.GetDiff("", c.ID(), define.DiffContainer)
 		if err != nil {
 			return errors.Wrapf(err, "error exporting root file-system diff for %q", c.ID())
 		}
diff --git a/libpod/define/diff.go b/libpod/define/diff.go
new file mode 100644
index 000000000..ee492eb3a
--- /dev/null
+++ b/libpod/define/diff.go
@@ -0,0 +1,26 @@
+package define
+
+// extra type to use as enum
+type DiffType uint8
+
+const (
+	// only diff containers
+	DiffContainer DiffType = 1 << iota
+	// only diff images
+	DiffImage
+	// diff both containers and images
+	DiffAll DiffType = 0b11111111
+)
+
+func (d DiffType) String() string {
+	switch d {
+	case DiffAll:
+		return "all"
+	case DiffContainer:
+		return "container"
+	case DiffImage:
+		return "image"
+	default:
+		return "unknown"
+	}
+}
diff --git a/libpod/diff.go b/libpod/diff.go
index c5a53478b..5bd162e7b 100644
--- a/libpod/diff.go
+++ b/libpod/diff.go
@@ -2,6 +2,7 @@ package libpod
 
 import (
 	"github.com/containers/common/libimage"
+	"github.com/containers/podman/v3/libpod/define"
 	"github.com/containers/podman/v3/libpod/layers"
 	"github.com/containers/storage/pkg/archive"
 	"github.com/pkg/errors"
@@ -21,14 +22,14 @@ var initInodes = map[string]bool{
 }
 
 // GetDiff returns the differences between the two images, layers, or containers
-func (r *Runtime) GetDiff(from, to string) ([]archive.Change, error) {
-	toLayer, err := r.getLayerID(to)
+func (r *Runtime) GetDiff(from, to string, diffType define.DiffType) ([]archive.Change, error) {
+	toLayer, err := r.getLayerID(to, diffType)
 	if err != nil {
 		return nil, err
 	}
 	fromLayer := ""
 	if from != "" {
-		fromLayer, err = r.getLayerID(from)
+		fromLayer, err = r.getLayerID(from, diffType)
 		if err != nil {
 			return nil, err
 		}
@@ -49,25 +50,30 @@ func (r *Runtime) GetDiff(from, to string) ([]archive.Change, error) {
 // GetLayerID gets a full layer id given a full or partial id
 // If the id matches a container or image, the id of the top layer is returned
 // If the id matches a layer, the top layer id is returned
-func (r *Runtime) getLayerID(id string) (string, error) {
-	var toLayer string
-	toImage, _, err := r.libimageRuntime.LookupImage(id, &libimage.LookupImageOptions{IgnorePlatform: true})
-	if err == nil {
-		return toImage.TopLayer(), nil
+func (r *Runtime) getLayerID(id string, diffType define.DiffType) (string, error) {
+	var lastErr error
+	if diffType&define.DiffImage == define.DiffImage {
+		toImage, _, err := r.libimageRuntime.LookupImage(id, &libimage.LookupImageOptions{IgnorePlatform: true})
+		if err == nil {
+			return toImage.TopLayer(), nil
+		}
+		lastErr = err
 	}
 
-	targetID, err := r.store.Lookup(id)
-	if err != nil {
-		targetID = id
+	if diffType&define.DiffContainer == define.DiffContainer {
+		toCtr, err := r.store.Container(id)
+		if err == nil {
+			return toCtr.LayerID, nil
+		}
+		lastErr = err
 	}
-	toCtr, err := r.store.Container(targetID)
-	if err != nil {
-		toLayer, err = layers.FullID(r.store, targetID)
-		if err != nil {
-			return "", errors.Errorf("layer, image, or container %s does not exist", id)
+
+	if diffType == define.DiffAll {
+		toLayer, err := layers.FullID(r.store, id)
+		if err == nil {
+			return toLayer, nil
 		}
-	} else {
-		toLayer = toCtr.LayerID
+		lastErr = err
 	}
-	return toLayer, nil
+	return "", errors.Wrapf(lastErr, "%s not found", id)
 }