Remove unused archive flag from diff commands

* Option left in images/diff.go CLI as comment implies it is needed for
  backwards compatibility.

```release-note
NONE
```

[NO NEW TESTS NEEDED]

Signed-off-by: Jhon Honce <jhonce@redhat.com>

5 files changed, 7 insertions, 17 deletions

diff --git a/cmd/podman/containers/diff.go b/cmd/podman/containers/diff.go
index e1a8ea729..15d3a3eff 100644
--- a/cmd/podman/containers/diff.go
+++ b/cmd/podman/containers/diff.go
@@ -32,13 +32,9 @@ func init() {
 		Parent:  containerCmd,
 	})
 
-	diffOpts = &entities.DiffOptions{}
+	diffOpts = new(entities.DiffOptions)
 	flags := diffCmd.Flags()
 
-	// FIXME: Why does this exists? It is not used anywhere.
-	flags.BoolVar(&diffOpts.Archive, "archive", true, "Save the diff as a tar archive")
-	_ = flags.MarkHidden("archive")
-
 	formatFlagName := "format"
 	flags.StringVar(&diffOpts.Format, formatFlagName, "", "Change the output format (json)")
 	_ = diffCmd.RegisterFlagCompletionFunc(formatFlagName, common.AutocompleteFormat(nil))
diff --git a/cmd/podman/diff.go b/cmd/podman/diff.go
index 7b78c8312..ec98fb5b5 100644
--- a/cmd/podman/diff.go
+++ b/cmd/podman/diff.go
@@ -35,9 +35,6 @@ func init() {
 		Command: diffCmd,
 	})
 	flags := diffCmd.Flags()
-	// FIXME: Why does this exists? It is not used anywhere.
-	flags.BoolVar(&diffOpts.Archive, "archive", true, "Save the diff as a tar archive")
-	_ = flags.MarkHidden("archive")
 
 	formatFlagName := "format"
 	flags.StringVar(&diffOpts.Format, formatFlagName, "", "Change the output format (json)")
diff --git a/cmd/podman/diff/diff.go b/cmd/podman/diff/diff.go
index a26502de9..15c55852a 100644
--- a/cmd/podman/diff/diff.go
+++ b/cmd/podman/diff/diff.go
@@ -13,7 +13,7 @@ import (
 	"github.com/spf13/cobra"
 )
 
-func Diff(cmd *cobra.Command, args []string, options entities.DiffOptions) error {
+func Diff(_ *cobra.Command, args []string, options entities.DiffOptions) error {
 	results, err := registry.ContainerEngine().Diff(registry.GetContext(), args, options)
 	if err != nil {
 		return err
@@ -63,7 +63,7 @@ func changesToTable(diffs *entities.DiffReport) error {
 	return nil
 }
 
-// IDOrLatestArgs used to validate a nameOrId was provided or the "--latest" flag
+// ValidateContainerDiffArgs used to validate a nameOrId was provided or the "--latest" flag
 func ValidateContainerDiffArgs(cmd *cobra.Command, args []string) error {
 	given, _ := cmd.Flags().GetBool("latest")
 	if len(args) > 0 && !given {
diff --git a/cmd/podman/images/diff.go b/cmd/podman/images/diff.go
index 13a8f1d9d..a017d569d 100644
--- a/cmd/podman/images/diff.go
+++ b/cmd/podman/images/diff.go
@@ -34,9 +34,7 @@ func init() {
 }
 
 func diffFlags(flags *pflag.FlagSet) {
-	diffOpts = &entities.DiffOptions{}
-	flags.BoolVar(&diffOpts.Archive, "archive", true, "Save the diff as a tar archive")
-	_ = flags.MarkDeprecated("archive", "Provided for backwards compatibility, has no impact on output.")
+	diffOpts = new(entities.DiffOptions)
 
 	formatFlagName := "format"
 	flags.StringVar(&diffOpts.Format, formatFlagName, "", "Change the output format (json)")
diff --git a/pkg/domain/entities/types.go b/pkg/domain/entities/types.go
index 5ae8a4931..3e6e54e7d 100644
--- a/pkg/domain/entities/types.go
+++ b/pkg/domain/entities/types.go
@@ -78,10 +78,9 @@ type InspectOptions struct {
 
 // DiffOptions all API and CLI diff commands and diff sub-commands use the same options
 type DiffOptions struct {
-	Format  string          `json:",omitempty"` // CLI only
-	Latest  bool            `json:",omitempty"` // API and CLI, only supported by containers
-	Archive bool            `json:",omitempty"` // CLI only
-	Type    define.DiffType // Type which should be compared
+	Format string          `json:",omitempty"` // CLI only
+	Latest bool            `json:",omitempty"` // API and CLI, only supported by containers
+	Type   define.DiffType // Type which should be compared
 }
 
 // DiffReport provides changes for object