I have a project that is currently licensed under the BSD 3-clause license, and I would prefer, going forward, to switch to the Apache 2.0 license. I plan on contacting the original contributors to see if they are willing to relicense their old code, but I am not counting on the majority of users doing so. However, this is not a major problem, since BSD and Apache 2.0 are compatible, so long as I retain the original copyright notice.

My question is, what's the best way to include the original copyright notice? Currently I have a single LICENSE file that includes the BSD 3-clause license. I'm planning on adding an AUTHORS file that will list all the contributors and which license their contributions are under (though this can also be inferred from the git history, if they haven't relicensed). The three obvious options are:

1. Two LICENSE files - LICENSE and LICENSE_OLD (or something like this)
2. A single LICENSE file containing both the Apache 2.0 and BSD license with a notice about which applies to which parts.
3. A LICENSE file containing the Apache 2.0 license, plus an included_licenses/ folder (or equivalent) that contains the BSD license (plus any other copyright notices necessary if I include code from other permissively licensed projects).

My preference would be #2, but my main worry there is that when you use standard boilerplate, it's easier for github or other programs to automatically categorize your project, and I fear that combining two licenses may cause problems down the line. #3 is fine but it does add a bit of clutter to the repo.

Are any of these approaches more standard than others? Are there any known tricky legal issues with any of them?

I have a project that is currently licensed under the BSD 3-clause license, and I would prefer, going forward, to switch to the Apache 2.0 license. I plan on contacting the original contributors to see if they are willing to relicense their old code, but I am not counting on the majority of users doing so. However, this is not a major problem, since BSD and Apache 2.0 are compatible, so long as I retain the original copyright notice.

My question is, what's the best way to include the original copyright notice? Currently I have a single LICENSE file that includes the BSD 3-clause license. I'm planning on adding an AUTHORS file that will list all the contributors and which license their contributions are under (though this can also be inferred from the git history, if they haven't relicensed). The three obvious options are:

1. Two LICENSE files - LICENSE and LICENSE_OLD (or something like this)
2. A single LICENSE file containing both the Apache 2.0 and BSD license with a notice about which applies to which parts.
3. A LICENSE file containing the Apache 2.0 license, plus an included_licenses/ folder (or equivalent) that contains the BSD license (plus any other copyright notices necessary if I include code from other permissively licensed projects).

My preference would be #2, but my main worry there is that when you use standard boilerplate, it's easier for GitHub or other programs to automatically categorize your project, and I fear that combining two licenses may cause problems down the line. #3 is fine but it does add a bit of clutter to the repo.

Are any of these approaches more standard than others? Are there any known tricky legal issues with any of them?