Over time, there have been enough issues that crop up with libgit2's fetching, either performance, lack of features, separate network configuration, etc that migrating to the CLI for fetching may be justified.

Gitoxide could eventually be an alternative but we then are still playing catch up with each new git feature.

The question is whether we should transition away from supporting libgit2 fetching.

Potentially related issues

• SSH key priority / failover on CircleCI+GitHub #10280
• Crates.io index update failing due to conflict with ~/.gitconfig #8172
• Unable to update registry crates-io #10230
• Cargo eating all RAM during aarch64 build under Docker on x86-64 #10583
• Cargo run is failing with "failed to set hostkey preference: The requested method(s) are not currently supported; class=Ssh" #14617
• cargo does not use git and fails to download, use default which makes sense #16803
• Support .ssh/config for specifying keys if ssh-agent fails #2078
• Git fetch fails via dumb-https protocol #8918
• cargo cannot read from local Git repositories with reftable #15184
• Cargo-update: exceedingly slow progress on update when local registry/index is used and git-fetch-with-cli is false #9167
• Cargo built-in Git/SSH client doesn't support @cert-authority #11577
• Private registry authorization stops working when Cargo's HTTP settings are changed #12524
• Cargo downloads git dependencies very slowly #13624
• SSL_connect: SSL_ERROR_SYSCALL behind a proxy #5256
• Add support for sparse git checkouts #11165
• Hang while updating git repository https://gitlab.com/jD91mZM2/no-std-compat #15481
• Cargo should reference git dependencies by commit hash instead of url #7497

Reported issues:

• Cargo internal error when downloading crate from git via ssh #16076
• Submodule of Git Dependency Hanging in Git CLI Mode #15775
• corrupt_git.rs tests (Migrate to CLI git fetching #17227 (comment))