Fix ClassesProcessor not whitelisting class files

[aoqia194]

Fixes #593!

This PR branch should probably be tested on the CLI against some other projects, because I am not sure if adding this second check will influence anything.

An explanation about the bug

When using --only=com/example, the com/example is marked as a whitelisted prefix; thus any directories in a JAR being matched against these whitelist prefixes will be created. However, when matching a singular class file (e.g. --only=com/example/MyClass), the original check against the to-be-created directory com/example would fail.

The check will boil down to:

"com/example".startsWith("com/example/MyClass")

and it is obvious that this would fail, thus the directory would not be created, and after decompilation happens and the class file is being dumped to a file, it will fail because of the parent directories not existing.

It took me a few hours to find a fix that didn't feel hacky, though I will admit that this still feels a little hacky and might have some unknown-to-me consequences. This simple change will affect this whitelist check and makes the check:

"com/example".startsWith("com/example/MainClass") || "com/example/MainClass".startsWith("com/example")

This check satisfies the directory-creating code and will create the directories just fine. Yippee!

[aoqia194]

I forgot to mention that it's also possible to just check the folders exist again right before writing the file, but I think this might be cheaper anyway? Also it may be better internally that these folders are marked as whitelisted in the first place.

[aoqia194]

I'm converting this to draft because this same issue has come up again on this branch despite this fixing it previously?

[aoqia194]

Ok it seems that this still works after checking, I think it was just user error with my vineflower wrapper. Maybe to prevent false-positives in the whitelisting with this extra check, we can also check for a suffix like .java or .class to determine whether a single file is being whitelisted or not? I don't think it's necessary right now however.