Add variable for global flags to runlabel command

[mheon]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind feature

Description

We need a variable in podman runlabel labels that expands to global Podman options, so we can pass through configuration (for example, storage config) to Podman commands being executed in labels.

Steps to reproduce the issue:

0. mkdir /tmp/new

1. podman --root=/tmp/new create --name test1 -t -i --label 'TEST=podman info'

2. podman --root=/tmp/new commit test1 testimg

3. podman --root /tmp/new container runlabel TEST testimg

Describe the results you received:

Podman uses the default storage root

Describe the results you expected:

Podman uses /tmp/new as a storage root

Ideal fix is something like $GLOBAL_OPTS we can throw in the label between podman and info to get the right options in there

[mheon]

@baude We discussed this via email, but the thread sort of died, so I'm throwing it up here

[rhatdan]

@baude Have you looked at this?
@QiWang19 Could you take a look at this?

[QiWang19]

@mheon I don't get the picture. Should the output of podman --root /tmp/new container runlabel TEST testimg be GraphRoot: /tmp/new?
like using podman --root=/tmp/new create --name test1 -t -i --label 'TEST=podman --root=/tmp/new info' instead of podman --root=/tmp/new create --name test1 -t -i --label 'TEST=podman info' ?

[mheon]

@QiWang19 runlabel reexecs a new Podman from the label set (TEST). We want to add a flag, say $GLOBAL_OPTS, that we can throw in TEST (for example, TEST=podman $GLOBAL_OPTS info), that expands to any global flags passed to Podman (storage options, log-level, syslog, etc)

[mheon]

Sorry, not a flag - a variable, similar to the other variables in runlabel

[mheon]

Once the variable is added, we then want the output of the last podman runlabel command to reflect the changed global options.