De-duplicate not needed certifications by cleaning the keyring after
import to remove old files when processing revocations. This basically
adds the functionality compared to import-clean.
libkeyringctl/keyring.py:
Simplify `convert_certificate()` by splitting out the conversion of
signature packets to `convert_signature_packet()` and the persistence of
packet material to `persist_key_material()`.
Add `convert_pubkey_signature_packet()`,
`convert_uid_signature_packet()` and
`convert_subkey_signature_packet()` to deal with the conversion of
public key signatures, UID signatures and subkey signatures
(respectively).
tests/test_keyring.py:
Add tests for `convert_certificate()`, `convert_signature_packet()`,
`convert_{pubkey,uid,subkey}_signature_packet()` and
`persist_subkey_revocations()`.
libkeyringctl/keyring.py:
Change `get_packets_from_path()` to use full conditional statements
which is easier to cover in tests.
tests/test_keyring.py:
Add simple tests for `get_packets_from_path()`,
`get_packets_from_listing()`, `export()` and `build()`.
tests/test_keyring.py:
Add tests for `is_pgp_fingerprint()`,
`transform_{fingerprint,username}_to_keyring_path()`,
`derive_username_from_fingerprint()` and get_fingerprints_from_paths()`.
tests/conftest.py:
Add `valid_fingerprint()` and `valid_subkey_fingerprint()` fixtures to
produce a generic "valid" PGP fingerprint string.
Add the `invalid_fingerprint()` fixture to generate a set of "invalid"
fingerprint strings.
CalledProcessError returns bytes for our invocations, the fix that
decoded bytes of stdout was purely to make the mocked test happy while
breaking the actual usage. Restore the behavior and fix the wrong mocked
data.
tests/test_sequoia.py:
Add unit tests for `keyring_split()`, `keyring_merge()`,
`packet_split()`, `packet_join()`, `inspect()`, `packet_dump()`,
`packet_dump_field()`, `packet_signature_creation_time()`, and
`latest_certification()`.
