podman ps can't be formatted by Label, but only by Labels

[bogdando]

kind bug

Description

podman ps can't be formatted by Label, but only by Labels, which breaks the docker CLI compatibility

Steps to reproduce the issue:

1. Create a container labeled with container_name=test

2. Try to filter it following docker CLI:

# podman ps -a --filter label=container_name=test --format '{{.Label "container_name"}}'
template: output:1:2: executing "output" at <.Label>: can't evaluate field Label in type shared.PsContainerOutput

# podman ps -a --filter label=container_name=test --format {{.Label "container_name"}}
too many arguments, ps takes no arguments

3. Try to filter it via Labels instead:

# podman ps -a --filter label=container_name=test --format {{.Labels.container_name}}
test

Describe the results you received:

--format '{{.Label "container_name"}}' is not working for podman, but works for docker

Describe the results you expected:

--format '{{.Label "container_name"}}' should also work for podman

Additional information you deem important (e.g. issue happens only occasionally):

Output of podman version:

Version:       0.10.2-dev
Go Version:    go1.10.2
OS/Arch:       linux/amd64

Output of podman info:

host:
  BuildahVersion: 1.5-dev
  Conmon:
    package: podman-0.10.1.3-2.git6e1aeb0.el7.x86_64
    path: /usr/libexec/podman/conmon
    version: 'conmon version 1.12.0, commit: 097cf71375bd18454d1c48b9fdf8ccff2ed995f8-dirty'
  Distribution:
    distribution: fedora
    version: "28"
  MemFree: 11450249216
  MemTotal: 12590895104
  OCIRuntime:
    package: runc-1.0.0-56.dev.git78ef28e.fc28.x86_64
    path: /usr/bin/runc
    version: 'runc version spec: 1.0.1-dev'
  SwapFree: 0
  SwapTotal: 0
  arch: amd64
  cpus: 3
  hostname: localhost.localdomain
  kernel: 4.18.7-200.fc28.x86_64
  os: linux
  uptime: 5h 12m 50.5s (Approximately 0.21 days)
insecure registries:
  registries: []
registries:
  registries:
  - docker.io
  - registry.fedoraproject.org
  - quay.io
  - registry.access.redhat.com
  - registry.centos.org
store:
  ContainerStore:
    number: 125
  GraphDriverName: overlay
  GraphOptions:
  - overlay.mountopt=nodev
  - overlay.override_kernel_check=true
  GraphRoot: /var/lib/containers/storage
  GraphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
  ImageStore:
    number: 3
  RunRoot: /var/run/containers/storage

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

[EmilienM]

Workaround here: https://review.openstack.org/#/c/614290/

[baude]

are we good to close?

[EmilienM]

@baude yes if you never change it or it'll break our code

[EmilienM]

@baude please close