Full support for .tar.gz files in the local repo

In my quest to use packrat to track a third party package I came across a pain point. I have a local .tar.gz file of a package source that I want track. We'll call it "my_package.tar.gz"

• I made a local repo folder "~/R/external"
• I added the local repo to the packrat options via set_opts()
• I added the local my_package.tar.gz to the local repo
• Next, i did a local_install on my_package.tar.gz and viola! My package is in the local packrat lib as expected.

Finally, I tried to record a snapshot() of the project and was greeted with an error: "No package 'my_package' found in local repositories specified". Looking at packrat's source this seems to be caused by the findLocalRepoForPkg() not recognizing .tar.gz files in the local repo.

Is this the preferred behavior?
If so, how should one snapshot local .tar.gz packages?

Start by tracing findLocalRepoForPkg() and the snapshot() and local_install() entry points involved in the reported sequence. Reproduce the local repository setup with my_package.tar.gz, then determine whether snapshot() can locate and record the package; done means the intended behavior is established and the reproduction either succeeds or has a documented resolution.