rust hook requires --path attribute

[zimbatm]

Cargo has changed how packages get installed and requires an extra --path <destination> attribute.

Symptom:

[INFO] Initializing environment for https://github.com/nix-community/nixpkgs-fmt.
[INFO] Installing environment for https://github.com/nix-community/nixpkgs-fmt.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
An unexpected error has occurred: CalledProcessError: Command: ('/nix/store/fcc3x8zwq1c0667xjs7bkn6ay8j4fdpz-rust-1.38.0-nightly-2019-08-07-ad7c55e1f/bin/cargo', 'install', '--bins', '--root', '/home/zimbatm/.cache/pre-commit/repoeft6xm6t/rustenv-default')
Return code: 101
Expected return code: 0
Output: (none)
Errors: 
    error: Using `cargo install` to install the binaries for the package in current working directory is no longer supported, use `cargo install --path .` instead. Use `cargo build` if you want to simply build the package.

I guess the fix should be done where here:

pre-commit/pre_commit/languages/rust.py

Line 87 in 9c6a1d8

'cargo', 'install', '--bins', '--root', directory, *package,

Do we want to make pre-commit compatible with multiple versions of cargo or just the latest one?

/cc @asottile @chriskuehl

[asottile]

heh that's annoying, yeah let's update to the latest install construct

[zimbatm]

I think the change would look like?

diff --git a/pre_commit/languages/rust.py b/pre_commit/languages/rust.py
index e09d007..c036739 100644
--- a/pre_commit/languages/rust.py
+++ b/pre_commit/languages/rust.py
@@ -84,7 +84,11 @@ def install_environment(prefix, version, additional_dependencies):
 
         for package in packages_to_install:
             cmd_output(
-                'cargo', 'install', '--bins', '--root', directory, *package,
+                'cargo', 'install',
+                '--bins',
+                '--root', directory,
+                '--path', directory,
+                *package,
                 cwd=prefix.prefix_dir
             )

This install the bin in the <directory>/bin folder

[asottile]

Seems right to me, there's pretty good tests for this so hopefully the test suite should agree 👍

[asottile]

The puzzling thing to me is why I can't reproduce this with our testsuite, we have a tiny little rust package that should also trigger this but doesn't seem to 🤔 -- I did figure out a fix though I'll add it to your PR 👍