Auto merge of #59681 - dtolnay:cargo, r=alexcrichton

Update cargo

20 commits in
63231f438a2b5b84ccf319a5de22343ee0316323..6f3e9c367abb497c64f360c3839dab5e74928d5c
2019-03-27 12:26:45 +0000 to 2019-04-04 14:11:33 +0000
- Fix Init for Fossil SCM project (rust-lang/cargo#6792)
- Fix member_manifest_version_error accessing the network (rust-lang/cargo#6799)
- Don't include email if it is empty (rust-lang/cargo#6802)
- Fix unused import warning (rust-lang/cargo#6807)
- Add some help and documentation for unstable flags (rust-lang/cargo#6791)
- Allow `cargo doc --open` with multiple packages (rust-lang/cargo#6803)
- Allow `cargo install --path P` to load config from P (rust-lang/cargo#6804)
- Add more suggestions on how to deal with excluding a package from a workspace (rust-lang/cargo#6805)
- Warn on version req with metadata (rust-lang/cargo#6806)
- cargo install: Be more restrictive about cli flags (rust-lang/cargo#6801)
- Support force-pushed repos with git-fetch-with-cli (rust-lang/cargo#6800)
- Cargo clippy (rust-lang/cargo#6759)
- Don't include metadata in wasm binary examples (rust-lang/cargo#6812)
- Update glossary for `feature` (rust-lang/cargo#6809)
- Include proc-macros in `build-override` (rust-lang/cargo#6811)
- Resolver: A dep is equivalent to one of the things it can resolve to (rust-lang/cargo#6776)
- Add some docs for `Downloads` (rust-lang/cargo#6815)
- Resolve: Be less strict while offline (rust-lang/cargo#6814)
- Accept trailing comma in test of impl Debug for PackageId (rust-lang/cargo#6818)
- Fix doc link (rust-lang/cargo#6820)

<br>

I specifically care about "Accept trailing comma in test of impl Debug for PackageId (rust-lang/cargo#6818)" to unblock https://github.com/rust-lang/rust/pull/59076.

Mentioning @ehuss.

src/tools/cargo

@@ -1 +1 @@
-Subproject commit 63231f438a2b5b84ccf319a5de22343ee0316323
+Subproject commit 6f3e9c367abb497c64f360c3839dab5e74928d5c