Show the output of failed scriptlets to the user

[m-blaha]

Currently, the output of RPM scriptlets is somewhat hidden in the log. This patch introduces a new libdnf5::base::Transaction::get_last_script_output() method, which returns the outputs of the most recently executed RPM scriptlet. This method is then utilized in the transaction callbacks in DNF5 to display the output to the user.

Although it would be more intuitive to add the scriptlet output as a new parameter in script_end and script_error, doing so would break the existing API.

The scriptlet output is only printed in the event of a failure; it is not displayed when the execution is successful.

Resolves: #522
Replaces: #1645

Changes:

5771571 (Marek Blaha, 5 minutes ago)
dnf5: Print rpm scriptlets outputs to the user

If a scriptlet fails, its output is displayed to the user in addition to
being written to the log. For scriptlets that complete successfully, the
output is only logged.

27d322a (Marek Blaha, 9 minutes ago)
transaction: Store outputs of the last rpm scriptlet

The outputs of the most recently executed RPM scriptlet in the transaction
are stored and can be accessed by the user through the
Base::Transaction::get_last_script_output() method.

55cf66f (Marek Blaha, 21 minutes ago)
rpm::transaction: Base::Transaction to callback holder

Handling scriptlet outputs requires rpm transaction callbacks to have
access to the libdnf5::Base::Transaction instance the rpm transaction
belongs to.

[jrohel]

Thank you for the PR. Just a minor change, please. See notes in review.

[jrohel]

Why is the string_view file included to the public header?
It is not used in this header. Please move the line to the transaction_impl.hpp file.

[m-blaha]

Thanks, I will fix it.

[jrohel]

I'm wondering if we need to make a copy in the future or if it would be better to just return a constant reference.
const std::string & get_last_script_output();
If you change here to a reference, change in transaction_impl.hpp as well

[m-blaha]

Yes, I intended to make a copy here. The thing is that this string is regularly changed from another thread and I wanted to ensure that the string the client received will remain the same.

[jrohel]

If the user calls get_last_script_output in a script_error or script_stop callback, the script has already finished and a new script will be started after the next script_start callback. The rpm executes scripts serially (there is no parallelization). So the contents of the string should not change while the script_error and script_stop callbacks are being serviced. And if the user needs to keep it for longer, he will make his own copy.

Your solution allows the user to call the get_last_script_output method from another thread. We don't generally support multithreading - it is not supported by the libraries used, for example libsolv. So I still don't know if this copy will help us in the future. But I will merge it.

[m-blaha]

I was specifically thinking about situations where the client keeps the output longer then during script_start/script_end execution. You are right that it can be handled on the client side. Thank you.