fix: handle unpadded base32/base64 digests and improve defaults

[maeb]

Fixes #90

[Copilot]

Pull request overview

This PR addresses WARC digest interoperability by accepting unpadded Base32/Base64 digests during decoding and updating default digest generation to avoid padding characters (per current WARC community guidance), while also switching defaults to stronger hashing.

Changes:

• Strip Base32 padding on encoding and accept missing padding on Base32/Base64 decoding.
• Update default digest algorithm to sha256 and default encoding behavior to “spec-recommended per algorithm” (SHA-1 → Base32, others → Base16).
• Refresh/extend tests to reflect the new digest defaults and unpadded Base32 support.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
digest.go	Implements no-padding Base32 encoding, tolerant Base32/Base64 decoding, and algorithm-based default encoding selection when unset.
options.go	Changes default digest algorithm to sha256 and default digest encoding to “unknown” (resolved later).
digest_test.go	Updates expected Base32 outputs (no padding) and adds tests for unpadded Base32 behavior.
record_test.go	Updates expected revisit-record digests to match new default digest algorithm/encoding.
unmarshaler_test.go	Updates expected computed digest headers when missing digests are auto-added under new defaults.

Comments suppressed due to low confidence (1)

digest_test.go:172

• The new Base64 unpadding support in DigestEncoding.decode (and the updated detectEncoding logic for no-padding Base64) isn't covered by tests here. Adding a valid Base64 unpadded case (and ideally a detectEncoding case for an unpadded Base64 digest length) would prevent regressions in the new behavior.

		{
			name:      "valid Base32 unpadded",
			encoding:  Base32,
			input:     "BT7V3XGGA4OVPYPVNTNJUMTXGY",
			wantError: false,
		},
		{
			name:      "valid Base64",
			encoding:  Base64,
			input:     "CY9rzUYh03PK3k6DJie09g==",
			wantError: false,

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Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

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Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

digest_test.go:125

• Typo in test case names: "lovercase" should be "lowercase".

		{"lovercase base32 encoding", "Some content", "sha1:t4ng5t3u5h43dlss5dvvqhkcbzr6qrj2", true},
		{"lovercase base64 encoding", "Some content", "sha1:nxpuz3tp+bguuujrwb1cdmporto=", false},

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