Make getTag() protected

[GrahamBorland]

There doesn't seem to be a way for a custom Tree implementation to provide its own tag-generating logic. Tree.getTag() is package-visible so can't be overridden by an external Tree. The result is that the tag is always null unless each logging call is preceded by Timber.tag().

Would it be a good (or bad) idea to make Tree.getTag() protected?

[kjsolo]

I also need it

[nathanjones]

It would be really nice to simply set the tag to whatever the calling class is in a custom Tree without having to recreate the logic in the DebugTree.

[kylemallory]

If there is a reason this isn't protected, some kind of acknowledgement and/or explanation would be super helpful.

[fougere-mike]

I would also like to be able to supply a tag from a custom Tree implementation.

[magillus]

I could use that functionality and PR looks good for this.

[AfzalivE]

Please @JakeWharton 4.7.2 needs this