Bump git2 from 0.20.4 to 0.21.0

[dependabot]

Bumps git2 from 0.20.4 to 0.21.0.

Changelog

Sourced from git2's changelog.

0.21.0 - 2026-05-18

0.20.4...main

Added

• Added experimental SHA256 repository support behind the new unstable-sha256 Cargo feature, along with *_ext API variants that accept an ObjectFormat. #1206
• Added opts::set_cache_max_size() and opts::get_cached_memory(). #1188
• Added Repository::object_format() and a new ObjectFormat enum. #1204
• Added Repository::set_config(). #1208
• Added merge_file() along with MergeFileInput. #1210
• Added Repository::refdb_compress() for packing loose refs. #1221
• Added public Refdb type, along with Repository::refdb() and Repository::set_refdb(). Repository::refdb_compress() now delegates to Refdb::compress(). #1228
• Added Revspec::into_objects(). #1230
• Added BlameHunk::final_committer(), BlameHunk::orig_committer(), BlameHunk::summary(), and BlameHunk::summary_bytes(). #1231
• Implemented Clone for Reference. #1233
• Added Repository::author_from_env() and Repository::committer_from_env(). #1237
• Added impl From<Utf8Error> for Error. #1239

Changed

• ❗ The ssh, https, and cred Cargo features are no longer enabled by default. Previously default = ["ssh", "https"]; now default = []. Enable them explicitly if you rely on credential helpers or transport support. #1168
• ❗ CredentialHelper and the url dependency are now gated behind the new cred Cargo feature. Enabling ssh or https transitively enables cred. #1168
• ❗ Updated to the 2021 edition. #1173
• ❗ Many string accessors that previously returned Option<&str> now return Result<&str, Error> or Result<Option<&str>, Error>, so callers can distinguish a missing value from a non-UTF-8 one. #1241
• ❗ BlameHunk::final_signature, BlameHunk::final_committer, BlameHunk::orig_signature, and BlameHunk::orig_committer now return Option to avoid segfaults when signature information is missing. #1254
• Bumped requirement to libgit2-sys 0.18.4, which updates libgit2 to 1.9.3.

... (truncated)

Commits

• dffaf27 Merge pull request #1256 from weihanglo/changelog
• 84b9c76 docs: changelog for git2@0.21
• 8c6dc4a Merge pull request #1206 from weihanglo/sha256-git2
• 7bd145e fix: import ObjectFormat in one place
• fc8af6a test(oid): split _ext to test each format separately
• b9bde87 test: oid length sanity check
• 57a68e0 feat(oid): impl Display for ObjectFormat
• 7acee09 chore(ci): test git2 sha256 support
• bdf5b7b fix: init example with --object-format option
• 9fb4e6a refactor(util): drop unsafe from zeroed_raw_oid
• Additional commits viewable in compare view

Note
Automatic rebases have been disabled on this pull request as it has been open for over 30 days.

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