fix: respect update_before_build=False during builddep (issue#1420)

[xsuchy]

dnf5 builddep upgrades already-installed packages even when update_before_build is disabled. Work around this by excluding all installed package names from repo lookups during dependency installation, so only genuinely missing packages are pulled in.

Fixes: #1420

[gemini-code-assist]

Code Review

This pull request implements a workaround for a DNF5 issue where packages are upgraded during build dependency installation even when update_before_build is disabled. It introduces a _get_update_exclude_opts method to generate an exclusion list of installed packages. Feedback suggests restricting this logic to DNF5 for compatibility, improving error handling for the RPM query command, and adding the @tracelog decorator to maintain consistency with the rest of the codebase.

[gemini-code-assist]

The new _get_update_exclude_opts method has a few issues that should be addressed:

1. Compatibility: It uses a comma-separated list for --exclude, which is a DNF5-specific feature. Standard DNF (DNF4), Yum, and MicroDnf do not reliably support comma-separated lists for this option and typically require multiple --exclude flags. Since this workaround is specifically targeting a DNF5 issue, it should be restricted to when DNF5 is the active package manager.
2. Robustness: The return code of the rpm -qa command is ignored. If the command fails (e.g., due to a corrupted RPM DB), out might contain error messages which would then be incorrectly parsed as package names.
3. Observability: The method is missing the @traceLog() decorator, which is consistently used throughout this class for debugging and tracing.
4. Python 3.6 Compatibility: While not an issue with the current implementation (which uses a single string), if you were to switch to multiple --exclude flags, be aware that Python 3.6 (still used on RHEL 8) has a limit of 255 arguments for function calls using *args. Using a single comma-separated string for DNF5 avoids this, but limiting the logic to DNF5 is safer.

@traceLog()
    def _get_update_exclude_opts(self):
        """
        When update_before_build is disabled, return --exclude options for all
        installed packages so that builddep/install won't upgrade them.
        Works around https://github.com/rpm-software-management/dnf5/issues/1747
        """
        if self.config.get('update_before_build', True):
            return []

        # This workaround is specifically for DNF5 behavior. 
        # Comma-separated excludes are also a DNF5-specific feature.
        if self.buildroot.pkg_manager.name != 'dnf5':
            return []

        command = [self.config['rpm_command'], "-qa", "--queryformat", "%{NAME}\\n",
                   "--root", self.buildroot.make_chroot_path()]
        out, status = self.buildroot.doOutChroot(command, returnOutput=True,
                                                printOutput=False, shell=False)
        if status != 0:
            return []

        pkg_names = set(filter(None, out.strip().splitlines()))
        if not pkg_names:
            return []
        return ['--exclude=' + ','.join(sorted(pkg_names))]

References

1. Adhere to the repository's use of @tracelog for method tracing and ensure compatibility across supported Linux platforms (including those using older package managers like Yum or DNF4). ^(link)

[xsuchy]

Addressed the the compatibility by doing this for DNF5 only.

[praiskup]

I don't really like this giant "--exclude" option, please lemme reiterate the problem with dnf.