Allow multiple commits in the same tar file

[git-hyagi]

closes: #366

[patchback[bot]]

Backport to 2.3: 💚 backport PR created

✅ Backport PR branch: patchback/backports/2.3/af48dec67f43da681deca587b4ff731800d81a58/pr-367

Backported as https://github.com/pulp/pulp_ostree/pull/370

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