A `.keep` file in the `objects/pack` directory acts as a lock to ensure that
operations like `git gc` do not clean up `.idx` files while a fetch is being
performed. It is safe to remove the `.keep` file once a fetch has completed and
a reference points to a given object in the packfile.
To ensure this happens in `radicle-fetch`, a newtype `Keepfile` is introduced.
It uses special `Drop` semantics by attempting to remove the file when the
object is dropped -- logging a warning if it fails to do so.
`FetchState` is augmented to keep a set of the `Keepfile`s. This ensures that
when the fetch completes, either successfully or with a failure, when
`FetchState` is dropped then so are the `Keepfile`s.
We ensure that the expected behaviour of removing the `.keep`files occurs by
adding a check in `e2e::test_replication` to check Alice's repository's packs.
Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett