Auto merge of #77952 - ehuss:update-cargo, r=ehuss

Auto merge of #77952 - ehuss:update-cargo, r=ehuss

Update cargo

11 commits in 9d1a4863abd9237dbf9d1b74c78632b6a205f6bb..12db56cdedbc2c26a9aa18f994c0188cdcc67df5
2020-10-05 18:29:52 +0000 to 2020-10-14 23:07:45 +0000
- Reinstate CARGO_PRIMARY_PACKAGE (take 2) (rust-lang/cargo#8758)
- Add actionable help message for --features (rust-lang/cargo#8773)
- Fix panic in `cargo doc` with -Zfeatures=itarget (rust-lang/cargo#8777)
- Update git2. (rust-lang/cargo#8778)
- Document RUSTFMT environment variable (rust-lang/cargo#8767)
- Update crossbeam-utils requirement from 0.7 to 0.8 (rust-lang/cargo#8769)
- Update toml dependency (rust-lang/cargo#8772)
- Mark proc-macro crates (rust-lang/cargo#8765)
- cargo-tree: mention special target `all` in CLI help text (rust-lang/cargo#8766)
- Bump to 0.50.0, update changelog (rust-lang/cargo#8764)
- Update deprecated GitHub add-path in workflows. (rust-lang/cargo#8760)