Facilitate exclusions by leveraging the "find" command

[pinacoelho]

On unix systems: Instead of using java to scan the filesystem, use "find", launched from java, to enumerate the files you're going to scan.

Advantages:

• Doesn't follow symlinks
• Can reliably stop at filesystem boundaries (-xdev)
• Will reduce the memory consumption of the java process
• All unixes have it

[xeraph]

I will document how to use find command with log4j2-scan -f option. :D