Update clippy via commit hashes instead of version numbers

[oli-obk]

fixes #888

[oli-obk]

We should NOT merge this until we know whether this will be a problem for the rls submodule in rustc. With clippy master I am getting

the cargo feature edition requires a nightly version of Cargo, but this is the beta channel

I fear that even though clippy is an optional dependency, this might still be hit

waiting for rust-lang/rust#51322 to come to any conclusion

[nrc]

the cargo feature edition requires a nightly version of Cargo, but this is the beta channel

How is this happening? Is this due to an update in Clippy so we'd be hit when we got the version with that in or is it inherently due to changing to a rev rather than a version? It seems weird that we get a Cargo error like this even when not including Clippy (which presumably we aren't in the Rust repo).

[oli-obk]

I don't know if you'd hit this. But the rustc repo is hitting it just with clippy, because it uses the previous beta cargo to build all its crates.

This is happening because clippy is on the 2018 edition

[Xanewok]

@oli-obk looking at rust-lang/rust#51322 and rust-lang/rust#51410 I assume everything is in order and we're safe to switch over to pinning clippy to a commit hash?

[oli-obk]

I want to try updating the clippy submodule before we go ahead with this

[oli-obk]

We need to wait for the next beta branch in order to update the stage 0 cargo

[mati865]

If rust-lang/rust#51122 gets merged this PR will need updating.
If everything goes fine rust-lang/rust#51677 will be unblocked.

[matklad]

Obsoleted by 6b4238b