feat(dev): add rustfmt checks in linter (#4989)

.pre-commit-config.yaml

@@ -86,4 +86,12 @@ repos:
         language: script
         entry: tools/git/test-affected-targets.sh
         stages: [push]
+    -   id: rustfmt
+        name: Format w/ rustfmt
+        description: Runs `rustfmt` on Rust files
+        language: system
+        entry: rustfmt
+        args: [--config-path, tools/rust/rustfmt.toml, --check]
+        types: [rust]
+        exclude: '^(kythe/proto/.*|third_party/.*)'
 exclude: '(.*/testdata/.*)|(third_party/.*)|(tools/platforms/configs/(versions.bzl|default_toolchain_config_spec_name/.*)$)'

kythe/release/cloudbuild/pre-commit/Dockerfile

@@ -47,6 +47,12 @@ RUN curl -s https://api.github.com/repos/google/google-java-format/releases/late
         && /bin/echo -e '#!/bin/sh\nexec java -jar /usr/bin/google-java-format.jar "$@"' >/usr/bin/google-java-format \
         && chmod +x /usr/bin/google-java-format
 
+# Fetch the rustup installer and install the nightly standard toolchain
+RUN curl -o /tmp/rustup.sh --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs && \
+        /bin/bash /tmp/rustup.sh --default-toolchain nightly --profile default -y && \
+        /bin/bash -c "source $HOME/.cargo/env" && \
+        rm /tmp/rustup.sh
+
 # Install go wrapper script
 ADD go /usr/local/bin/go
 ENV PATH=$PATH:/root/go/bin

tools/rust/rustfmt.sh

@@ -17,5 +17,5 @@
 find kythe/rust/ tools/rust/ -name '*.rs' -not -wholename "*target/*" -not -wholename "*rust/*/testdata/*" -print0 | while read -r -d $'\0' f
 do
     echo "Formatting $f";
-    rustfmt --config-path "$(dirname "${BASH_SOURCE[0]}")" "$f";
+    rustfmt --config-path "$(dirname "${BASH_SOURCE[0]}")" "$@" "$f";
 done