oxidize cargo release

[Sebastian Thiel (Byron)]

• fetch (intentionally left to git command)
• revparsing
• merge base
• get branch for head commit
• is dirty (tracked and untracked)
• Diff between tag and head
• Commit
  • from worktree
• Tagging
• commit and tag signing
• Iterate over existing tags
• push (intentionally left to git command)
• Get working directory

Details can be found here: https://github.com/crate-ci/cargo-release/blob/master/src/git.rs

https://github.com/crate-ci/cargo-release

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Original issue: #312