Permit stacking multiple --offline commands for a single reboot.

[RokeJulianLockhart]

Currently, multiple transactions with --offline cannot be performed sequentially on the next reboot, even though some commands must be separated into separate invocations in order to execute.

discussion.fedoraproject.org/t/146811 provides an example of when this is necessary and elaborates on how this appears to a user:

Example

Say that I want to invoke the undermentioned with upgrade's offline flag appended: ¹

1. sudo dnf update @multimedia --setopt="install_weak_deps=False" --exclude=PackageKit-gstreamer-plugin

2. #!/usr/bin/env sh
   sudo dnf swap mesa-va-drivers mesa-va-drivers-freeworld && \
   sudo dnf swap mesa-vdpau-drivers mesa-vdpau-drivers-freeworld

Desire

However, I want to invoke them in the same sudo dnf5 offline reboot transaction.

Rationale

1. I don't wish to reboot for each command.
2. Attempting to stack them sequentially like one would a series of pre-authenticated -ys invokes offline clean for each subsequent invocation.

discussion.fedoraproject.org/t/146811/2 responds, confirming that this doesn't actually appear to be possible with DNF5:

Running multiple dnf {install/upgrade/swap/etc} commands with the --offline option is not a solution, as you might have already experienced, since upon running the second command (without rebooting), the first one will be cancelled:

There is already an offline transaction queued, initiated by the following command:
	dnf swap mesa-va-drivers mesa-va-drivers-freeworld --offline
Continuing will cancel the old offline transaction and replace it with this one.

It seems that dnf only accepts one offline transaction at a time. Stacking offline transactions would make sense, though.

Consequently, I suggest that this functionality be implemented, for without it, performing multiple transactions offline is an exercise in wasted time.

Footnotes

1. rpmfusion.org/Howto/Multimedia ↩

[m-blaha]

This seems like a use-case for the "do" command - currently exists as a draft PR - #2089
Although there still will only be one offline transaction, with do --offline command it can contain multiple install/remove/upgrade operations.

[RokeJulianLockhart]

Although there still will only be one offline transaction

@m-blaha, do you mean that everything shall need to be defined in one command, or that _execute shall execute everything staged in a single reboot, in that special SystemD state? If the latter, that's what I desire.

Additionally, have you any idea what the proposed syntax would be? I've read #1223 (comment), but it's rather too project-specific for a lay man like me to comprehend. I've a mind to mark this issue as a duplicate of it, if you agree that it is.

[m-blaha]

I guess the former one. There still will be only one offline transaction prepared and later executed after dnf offline reboot.
But the transaction would be prepared using a command like dnf do --action=upgrade @multimedia --action=remove mesa-va-drivers mesa-vdpau-drivers --action=install mesa-va-drivers-freeworld mesa-vdpau-drivers-freeworld --offline.

So this is definitely not a duplicate of #1223 .