[hadd] Improve verbosity settings

[silverweed]

New verbosity works like this:

v0: only output errors
v1: only output errors and warnings
v2: output errors, warnings and TFileMerger messages
v3: output all messages

This is largely backwards-compatible as the default verbosity was and still is 99.

One message (and one error!) were for some reason only emitted when verbosity was exactly 1, which makes no sense. This PR changes it to a regular Info() and Err() respectively. This means that by default hadd will now emit an additional message at the end of the merging process.

Checklist:

• tested changes locally
• updated the docs (if necessary)

This PR fixes #19479

[github-actions]

Test Results

    21 files      21 suites   3d 23h 23m 48s ⏱️
 3 646 tests  3 494 ✅  0 💤 152 ❌
74 819 runs  74 649 ✅ 18 💤 152 ❌

For more details on these failures, see this check.

Results for commit 55e7f1d.

♻️ This comment has been updated with latest results.

[dpiparo]

Thanks for putting some order in this!

[pcanal]

This is a step in the right direction. I believe that we need more flexibility for the Info message, I proposed a solution (that still need more update to Info calls).

[pcanal]

See previous comment.

[silverweed]

I agree on adding the multiple levels to Info(), but what about all the messages you didn't correct? Are those all 2? Or 3?
If, as the description says, 2 is only for "minimal informative messages", I would expect most messages to be at level 3, but that would change what is shown by default if we set the default to 2...

[pcanal]

I think that 2 is for "minimal informative messages", is the 'right' default.

I already made some proposition inline, here is another stab:

601:         Info(2) << "added " << nObjects << " object from filter file '" << *filterFileName << "'\n"; 
647:      Info(2) << "parallelizing  with " << nProcesses << " processes.\n";
678:      Info(2) << "target file: " << targetname << "\n";
681:      Info(3) << "Using " << cacheSize << "\n";
763:         Info(2) << "compression setting for meta data: " << newcomp << '\n';
765:         Info(2) << "compression setting for all output: " << newcomp << '\n';
784:      Info(2) << "each process should handle at least 3 files for efficiency."
897:         Info(3) << "merged " << allSubfiles.size() << " (" << fileMerger.GetMergeList()->GetEntries()

[pcanal]

LGTM. Thanks.