Retention fix

[gazpachoking]

Addresses issues in #195

• Ensures directories are never deleted when handling retention
• Ensures log extension is included in filenames when handling retention

[gazpachoking]

Oops, should have run the tests locally before submitting. Requiring the dots was the one thing I knew could be made more specific, and is what's causing the failure right now. I was trying to avoid changing too much, I think to make it better we need multiple glob patterns.

[Delgan]

Thanks for the PR!
I guess it's just a small edge case, a fix is probably possible while keeping just one glob pattern. I will take a look.

[Delgan]

@gazpachoking Ok, you was totally right, multiple glob patterns are required.

I took the liberty of making changes to your branch as a result of this PR, I hope you don't mind.

While refactoring the code, I decided to combine the glob pattern with a regex check which I think is more permissive: we want to match "file.2020-01-01_01-01-01_0000001.log" (automatic renaming on rotation), but we want to exclude both "file.foo.log" and "foo.file.log" which is complicated without regex.

At the same time, I realized it was wrong to call os.path.splitext() after glob.escape() as it would result in something like ("file\\", ".log"), so I modified the corresponding code.

Also, I tried to fix a 100%-theoretical bug that could occur if "." was present in the {time} spec format (leading to wrong splitext()).

This results in code much more convoluted unfortunately, but this should greatly reduce false positives during retention process. Does it look good to you?

[gazpachoking]

It is a bit hard to read and understand the glob and regex bit, but the expanded test suite is clear, and makes me confident it's doing what it's supposed to now. 👍

[Delgan]

Great, thanks for the review! Let's merge it then. ;)