podman: podman save fails when specifying an image using a digest

/kind bug

Description

podman save fails when specifying an image using a digest

Steps to reproduce the issue:

1. podman pull quay.io/olmtest/single-bundle-index@sha256:dce3d3e858ecfb7f2ddfb0e3550a867faaf39706dfb6da71cab04f909edc428f

2. podman save quay.io/olmtest/single-bundle-index@sha256:dce3d3e858ecfb7f2ddfb0e3550a867faaf39706dfb6da71cab04f909edc428f -o temp.tar

Describe the results you received:

Error: error getting Docker archive ImageReference for “temp.tar:quay.io/olmtest/single-bundle-index@sha256:dce3d3e858ecfb7f2ddfb0e3550a867faaf39706dfb6da71cab04f909edc428f”: docker-archive doesn’t support digest references: temp.tar:quay.io/olmtest/single-bundle-index@sha256:dce3d3e858ecfb7f2ddfb0e3550a867faaf39706dfb6da71cab04f909edc428f

Describe the results you expected:

The archive should be created like the Docker CLI does.

Output of podman version:

Version:            1.7.0
RemoteAPI Version:  1
Go Version:         go1.12.14
OS/Arch:            linux/amd64

Output of podman info --debug:

debug:
  compiler: gc
  git commit: ""
  go version: go1.12.14
  podman version: 1.7.0
host:
  BuildahVersion: 1.12.0
  CgroupVersion: v1
  Conmon:
    package: conmon-2.0.10-2.fc30.x86_64
    path: /usr/bin/conmon
    version: 'conmon version 2.0.10, commit: 35d9b09d9d2791c7167091a9f25792535a380967'
  Distribution:
    distribution: fedora
    version: "30"
  IDMappings:
    gidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 10000
      size: 65536
    - container_id: 65537
      host_id: 100000
      size: 65536
    uidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 10000
      size: 65536
    - container_id: 65537
      host_id: 100000
      size: 65536
  MemFree: 282464256
  MemTotal: 8058654720
  OCIRuntime:
    name: runc
    package: runc-1.0.0-102.dev.gitdc9208a.fc30.x86_64
    path: /usr/bin/runc
    version: |-
      runc version 1.0.0-rc10
      commit: ffa084d279c26351e6e63bd2c3f28d43fa1f6e57
      spec: 1.0.1-dev
  SwapFree: 7726428160
  SwapTotal: 8384409600
  arch: amd64
  cpus: 4
  eventlogger: journald
  hostname: mprahl-laptop
  kernel: 5.4.17-100.fc30.x86_64
  os: linux
  rootless: true
  slirp4netns:
    Executable: /usr/bin/slirp4netns
    Package: slirp4netns-0.4.0-4.git19d199a.fc30.x86_64
    Version: |-
      slirp4netns version 0.4.0-beta.2
      commit: 19d199a6ca424fcf9516320a327cedad85cf4dfb
  uptime: 4h 33m 53.01s (Approximately 0.17 days)
registries:
  search:
  - docker.io
  - registry.fedoraproject.org
  - quay.io
  - registry.access.redhat.com
  - registry.centos.org
store:
  ConfigFile: /home/mprahl/.config/containers/storage.conf
  ContainerStore:
    number: 9
  GraphDriverName: overlay
  GraphOptions:
    overlay.mount_program:
      Executable: /usr/bin/fuse-overlayfs
      Package: fuse-overlayfs-0.7.5-2.fc30.x86_64
      Version: |-
        fusermount3 version: 3.6.2
        fuse-overlayfs: version 0.7.5
        FUSE library version 3.6.2
        using FUSE kernel interface version 7.29
  GraphRoot: /home/mprahl/.local/share/containers/storage
  GraphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "false"
  ImageStore:
    number: 19
  RunRoot: /run/user/1000
  VolumePath: /home/mprahl/.local/share/containers/storage/volumes

Package info (e.g. output of rpm -q podman or apt list podman):

podman-1.7.0-3.fc30.x86_64

Additional environment details (AWS, VirtualBox, physical, etc.):

physical