sl fails on shallow checkouts

[stepancheg]

Repro

$ git clone https://github.com/protocolbuffers/protobuf --depth 1
...

$ sl
reposetup failed in extension dirsync: When constructing alloc::boxed::Box<dyn commits_trait::DagCommits + core::marker::Send> from dyn storemodel::StoreInfo, "10-git-commits" reported error

Caused by:
    0: resolving 0fba21ab2187d1f9cb64041ec7c19c5286821049 to git commit
    1: object not found - no match for id (0fba21ab2187d1f9cb64041ec7c19c5286821049); class=Odb (9); code=NotFound (-3)
abort: When constructing alloc::boxed::Box<dyn commits_trait::DagCommits + core::marker::Send> from dyn storemodel::StoreInfo, "10-git-commits" reported error

Caused by:
    0: resolving 0fba21ab2187d1f9cb64041ec7c19c5286821049 to git commit
    1: object not found - no match for id (0fba21ab2187d1f9cb64041ec7c19c5286821049); class=Odb (9); code=NotFound (-3)

$ git fetch --unshallow
...

$ sl
@  21e9aa6cac  Yesterday at 22:04  tonyliaoss  origin/main
│  Add back UPB test coverage that was undone from test migration.
~

sl does not necessary have to support shallow clones, but it could provide a nice message with suggestion to git fetch --unshallow.