Update git2 requirement from 0.18 to 0.20

[dependabot]

Updates the requirements on git2 to permit the latest version.

Changelog

Sourced from git2's changelog.

0.20.4 - 2026-02-02

0.20.3...0.20.4

Fixed

• Fix undefined behavior when dereferencing empty Buf. #1213

0.20.3 - 2025-12-06

0.20.2...0.20.3

Changed

• Bumped requirement to libgit2-sys 0.18.3, which updates libgit2 from 1.9.0 to 1.9.2. #1197

0.20.2 - 2025-05-05

0.20.1...0.20.2

Added

• Added Status::WT_UNREADABLE. #1151

Fixed

• Added missing codes for GIT_EDIRECTORY, GIT_EMERGECONFLICT, GIT_EUNCHANGED, GIT_ENOTSUPPORTED, and GIT_EREADONLY to Error::raw_code. #1153
• Fixed missing initialization in Indexer::new. #1160

0.20.1 - 2025-03-17

0.20.0...0.20.1

Added

• Added Repository::branch_upstream_merge() #1131
• Added Index::conflict_get() #1134
• Added Index::conflict_remove() #1133
• Added opts::set_cache_object_limit() #1118
• Added Repo::merge_file_from_index() and associated MergeFileOptions and MergeFileResult. #1062

Changed

• The url dependency minimum raised to 2.5.4

... (truncated)

Commits

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